First we'll talk about Legacy. Takes place 130 years ABY. This one is by far my favorite.
I love how the lines seem to be more blurred in Legacy than in any other Star Wars comic (or movie for that mater). You don't just have good vs. evil; the light vs. the dark. You have the bad guys, the Imperials (and Imperial Knights), who seems to be mostly using the light side of the Force. You have the really bad guys, the Sith, who are all dark side, but of course now there's more than just two of them. You have the good guys, the new Rebellion, who have no help at all from Force users, except the very shakey alliance they have formed with the Imperials for the sake of uniting against their common enemy the Sith. You have the sort of good guys, which is Cade Skywalker and his crew. Cade's intentions are good, but his methods are very dark side. Then you have the Jedi, who I guess are the good guys, but they prefer to remain in hiding and not get involved in anything. They don't seem to want to fight any wars, and who can blame them…we all know how that turned out when they got involved in the Clone Wars.
John Ostrander has really outdone himself in weaving a compelling story out of this.
Okay, I said too much there. It's a good comic, take my word for it.
Dark Times is awesome awesome awesome. It almost got canceled, but a loyal fan base keeps it going. It takes place right after Episode III. It has Vader, which is why I dig it, but it also follows a Jedi, Daas Jennir, who escaped Order 66, as well as Bomo Greenbark, whose family was destroyed thanks to the empire. At first I was skeptical of this cast of basically nobodys, but they have really done something with it. It's good.
Dark Times spun out of Star Wars Republic (written by John Ostrander), which chronicled the Clone Wars, so look for Republic in trade format. I think there are something like 7 volumes(?)
Rebellion was canceled recently. Poo. I like Luke stories, but they were starting to get stale after the Sunber storyline. Look for it in trade format. Rebellion spun off of Empire, so you can also look for Empire in trade format. Again, there's about 7 to 10 volumes. Again, some good Vader stories in Empire.
Knights of the Old Republic is admittedly my least favorite, but I'm still a loyal reader. I think it's the art that bugs me the most about it. The stories and writing for the most part are solid. But if you are a fan of the era, it's a must read. I believe it takes places a few years before the video game.
There's also the Clone Wars comic, but it's more aimed at kids and certainly not as cool as the tv show. This was planned as a 6-issue miniseries, and they are currently on issue 4.
Recently announced was Star Wars Invasion, coming to comic shops in July, which will take place in the New Jedi Order era. (are you familiar with the timeline of the books/novels?) The art I have seen so far looks amazing.
That about covers it, unless you want to go back into the archives. In that case, Dark Horse is continuing to release Omnibus editions, which collects just about everything Star Wars they've ever published. I think they have 10 omnibuses so far.

I can find it in the mega-super-nobody wants clearence rack for $1 any day now to add it to my collection
