When hopping from planet to planet and trading start to feel repetitive, and you're not in the mood for quests, you might want to visit or do some of the following:
Gun and rifle training on Manurhin Edit
Manurhin (Vichy System) features a shooting range for gun and rifle training. Here you can raise your two shooting skills up to decent levels without risking your (ascii) life. Some training is badly needed if you're interested in accepting assassination missions.
Use a laser gun and a laser rifle for training so not to waste lots of expensive ammo. (Remember that all rifles require your other hand to be empty, you can't aim properly otherwise.) Start with the left, shorter ranges, then, when you consistently score around 80 to 90 points switch to the longer range targets. Your skill increases faster the further away your target is, but only if you actually hit.
If you'd also like to train your throwing skill while you're at it buy 6 smoke grenades and lob them down the street as far as possible. Wait until the smoke clears, rinse and repeat. This is safe, even if you accidentally hit someone. (Of course you don't have to be on Manurhin to do that.)
Unfortunately there is no way to train unarmed and armed melee fighting safely. But you can at least avoid the murder penalty by scooping up ejected Pirate and Retro pilots after you or someone else blew up their ships. That way you can fight one enemy at a time without bystanders or bodyguards interfering. (You can actually set up your ship for scooping, i.e. 10 KPS, heading for the escape pod, then leave the console, switch to combat mode and press [W] repeatedly until the 'victim' appears.)
Carry as little as possible, weight slows you down; consider leaving things you don't immediately need on the floor. Hide behind your ship's cockpit door until they're directly on the other side. That way you can close to melee range before they can fire a shot. If you're only wearing a NanoComp Vest and a helmet and wielding a Stunrod you're often fast enough to zap them twice before they can do anything. Once armed fighting skill has been trained high enough that your Stunrod hits with 100% you can stun most opponents before they get a single chance to move.
After they're stunned, stab them with a knife (trains better than a Vibroblade) or hit them bare-handed to improve armed and unarmed fighting skills respectively. Don't forget to save your game often, at the outset immediately before each fight. Even with an opponent on board you can still land and save as long as you haven't switched to combat mode yet.
Gambling on the Lucky Lady Edit
The Lucky Lady is the beautiful casino ship found in the Adavene System. Here you can play Roulette, Black Jack, Video Poker or Slots. Don't expect to get rich, but it sure is fun, and as long as you keep your stakes low you won't lose too many credits, either.
Even though the Lucky Lady is heavily guarded it is very well possible to destroy it if you fly a powerful enough ship. However, as you can't gamble anymore afterwards, why would anyone want that?
Bureaucracy of Port NewtonEdit
The capital planet Port Newton is located in the Loye System. It features the large government building with long rows of counters where you can pay your outstanding fines. Even if you haven't murdered anyone, try it at least once.
The Prison BaseEdit
The prison base Trou is located in the Bastille System. After you've earned some reputation the Mercenaries Guild will offer you bounty hunting missions. If you capture some criminals alive you'll have to bring them to this prison base to cash in the bounty.
The Research FacilityEdit
The Acorn Research Facility is found in the Alabaster System. (Caveat: Plexus Minor is not Confed controlled.) There is not that much to see yet, just a rude clerk behind a counter who you can talk to and two guards in front of locked doors. The quest A Lady in Trouble - Part 2 partly takes place here, and maybe some future Ascii Sector release will fill this place with life?
The Shopping Mall Edit
New Frankfurt in the New Frankfurt System features a cute little mall with three shops and a restaurant. You can talk to each of the shopkeepers as well as the waitresses, however it's not possible to buy anything. This is another location waiting for some quest or future Ascii Sector version to expand upon the interaction.
Pole Dancer on IridionEdit
Looking at NPCs via the [L] key shows them all exactly the same, regardless of gender, varying only in equipment. Except there is one who is ... different: the Pole Dancer on Iridion (Zepyranth System, not Confed controlled).
Naming your own character "Pole Dancer" when starting the game exposes (pun!) a hilarious (anatomical) bug when looking at yourself with the [E] key, whereas the Autodoc booths' scanners display this unintended easter egg correctly.
Visiting the PiratesEdit
The pirates have three bases: Bellamy in the Rynkel System, Munroe in TC-101 and Bounty in LV-426. Bellamy is the easiest to reach. Obviously your ship will have to be able to defend itself against around 6 attacking Talons ("V") before you can even think of visiting a pirate base (a fully equipped Galaxy ("X") should do; don't forget to save your game). If you happen to meet a Pirate fleet with one of their flagships, don't worry, they'll pursue their course and remain calm unless you shoot at one of them. However single Pirate ships not belonging to the group might attack at the same time, be sure not to confuse them. Once you've managed to land you can walk around like on any other base without being attacked by the NPCs. You can buy illegal merchandise like Ultimate here, which can earn quite a lot of money very quickly if you have a buyer.
Pirate bases are the only place where you can buy Hidden Compartments i.e. hide part of your cargo space from contraband searches. They cost 2000 credits per cargo unit, and the manual says as long as you hide less than 10% of your total space you should be safe from discovery. For transporting larger amounts of contraband just keep your travelling route short and hope they don't catch you.
Assassinating a target on a pirate base counts as killing a pirate, not as murder.
Raiding for Kilrathi WeaponsEdit
The elusive Kilrathi Gun and Kilrathi Rifle are powerful, though quite imprecise, and can hold 16 and 10 shots respectively. They would cost 4000 and 6000 credits, more than any other weapon in the game. The problem is you can't buy them anywhere, the only way to get them is taking them from a Kilrathi. But unlike Pirates or Retros their pilots never eject with escape pods, except sometimes Mercenaries mission characters.
Kilrathi fly two kinds of ships, Dralthi ("C") and Gothri ("D"). Both are dangerous; particularly Gothri are deadly and you should usually blow them up with missiles as fast as you can. But both are flown by a Kilrathi Pilot with a gun, and the Gothri additionally accommodates a Kilrathi Captain with a rifle, and they won't give their equipment to you voluntarily. If you have a single Kilrathi on its own try wearing it down until on at least one side the shield is completely gone, then fire 2-3 Disabler Missiles at it. If you have any, switch off your aft and side turrets so that you don't accidentially destroy your prey. Once the ship stops moving (cyan dot in center of target display turns gray) come to a halt next to it to board it (if you wait too long the crew may repair it). When you walk along the connection tube the Kilrathi will open the hatch and attack. Take them down quickly e.g. with a MPR-481 Pulse Rifle (after practicing!, see above) before they waste too much of the precious ammo - or kill you.
Unfortunately Kilrathi weapons are not suited for 'every day' use, not least because harvesting ammo in this way is too time consuming to be practical (unless you really go big and raid a Kamekh), but these hard-earned items are something you can be proud of.