Lots of things have changed for me from this site. The music forum has opened me up to a lot more good bands I probably wouldn't have heard of, the sig forums have increased my knowledge and skills in Photoshop..which might not seem like a lot but since Im doing multimedia, it could be the difference between a credit and a distinction just off a tutorial someone posted. The OTF has opened me up a bit more socially, and I've drastically changed since being in high school with regards to interacting with people. The movie forums have been good for broadening the scope of movies, just by looking at or being in particular discussions, again highly useful for my studying, theres a few threads in GDF about stuff happening in the world I wouldnt pick up on and just provoked more thinking into them, and the games forum has been good to mix with people sharing the same interests and different knowledge, which doesnt happen a lot for me in real life.
Not to mention everything thats happened off the forum that wouldnt have been possible, everyone who I've talked to in MSN etc, all the forums that were created from other members that have again expanded into other sources of interest and knowledge.
So yeah, its done quite a bit.