So, which one of you losers out there doesn't have a GBA? Quit reading this page, go to the store, and get one.
A little history: Nintendo dominated the handheld market in 1998 with it's Game Boy color, yet in 1999 and 2000 started to see some real competition from Bandai and Neo Geo, as well as emerging handhelds like the GP 32. So in 2000 they finally got around to giving us an update with some real muscle. Once again they made the wise choice of making the console backwards compatible with all GB titles, thus giving it an instant library of over 1000 compatible games. Finally, you can play your old GB games in color and actually see what you're doing. Sadly, yet again Nintendo was too cheap to give us a screen that was backlit.
So we had to wait another two years until they finally got around to releasing the GBA SP (which stands for "special".) Finally a Game Boy where you can see what's going on.
The first GBA was pretty decent, has four buttons (A & B plus L & R shoulder buttons,) it's laid out horizontally like a Game Gear and ergonomically fits into your hands. The only problem with it is the screen is a dim piece of crapola.
The SP is a lot more compact, folds away like a clam, and has a backlit screen. The only gripes I have with it is that the volume does not go up enough for my liking and OG carts stick out of the bottom (and could get damaged if say, I threw my SP across the room in rage after dying for the 417th time at R-type or something.) It's a lot smaller, so you neaderthals with big ass lumberjack hands may have a problem. This is one of the few game systems I actually broke down and bought new.
First edition GBAs are common as dirt, you can get them for as little as 10$. The SP is starting to phase out now as Nintendo is throwing all it's resources behind thier new DS console. There are by far way too many 3rd party periphials for me to even try to list here, so I'll just put a few of the cooler ones.