Forbidden island, definitely. I got it on ebay for cheap and it was awesome. Looks like, though, the lowest price I can see is around 30$. If you want, you can look at the instructions of sets on Peeron to se how they are built and see every feature and brick, so you know what you're buying.
I know. I mean, Lego does have some great sets theses days, but a lot of them flat out suck, and the ones that are great, while being great, have this... new.. feeling to them. Legos Before 2003 are teh pwnz. The old ones, have this great , you know, classic feel to them, with no fancy new pieces.
Luckily most of the core of my Lego C hoard is made up of old pieces.
I think you should save up just a little more and buy 6273 Rock Island Refuge. That was one of my favorite sets of all time. I saved the instructions and I've actually rebuilt it 3 times since I bought it in 1991.
I said "no" to drugs, but they just wouldn't listen...