Star Wars RPG
West End Games' Star Wars is a fun, easy-to-learn system. Because of this, people hate it and avoid it like the plague.
There were a lot of supplements and modules made for the system; you can see them all here.
The system:
Every character has six attributes: Strength (punchin' and liftin'), Dexterity (shootin' and dodgin'), Perception (lookin'), Knowledge (knowin'), Mechanical (drivin', bantha ridin'), and Technical (droid fixin'). These are rated by how many dice are in them; an average human character has a Strength of 3D, which means she rolls 3d6 every time she makes a Strength check.
Skills fall under attributes, and their dice are added to the attribute when making skill checks. For example, if you have a Dex of 4D and you put one point into Blasters, your Blasters skill starts at 5D.
NPC characters get 12D to divide between their attributes, and PCs (or important NPCs) get 18D. The minimum attribute rating for a human is 2D, and the max (for a human) is 4D.
One attribute die can be split up into bonuses applied to other attributes. You can split it up into three +1s or a +1 and a +2. The bonus is then applied to another attribute (so your Strength 4D becomes 4D+2, and all skills under it gain a +2. You can't put all three points into one attribute.
Skills are rated the same way as attributes, but the cap on a skill is 13D. Characters get 7D to put into skills at character creation. No more than 2 points can be put into a skill at creation.
You can take one point from your 7 starting skill points and use it to make 3 specializations for other skills. If you had Blaster Pistols 5D and used one of the specializations on it, you could have Blaster Pistols 5D (Heavy Blaster Pistols 6D).
Example:
If you have a bounty hunter character with a blaster skill of 5D, you roll 5d6 every time you shoot at something. If the GM decides that you rolled high enough to hit (usually 10-15 is good enough), the other character rolls a Strength check (and adds on any dice they get for wearing armor). If their roll's total is higher, they shrug it off; if the attacker's roll is higher, the victim gets hurt (and depending on how crappy they rolled, they might die).
D20 Star Wars
One could also ignore all the previous shit on this page and just play the Wizards of the Coast Star Wars, which is exactly like D&D. The only differences come from what version, there is a Saga Edition that's like 4th Edition of D&D (but it was around before 4E and is better) and there is an earlier edition "Revised" that plays the same as D&D 3.5.