I was wondering if there are exchange fees for using the MTGOX.com service to sell or buy bitcoins.
There are fees at nearly all exchanges. The fee for selling will vary as higher volumes get a lower rate. Starting out you are at 0.6%. There may be additional fees when withdrawing those funds as wel.. For instance, the least method is Dwolla at $0.25 per transaction. Wire transfers are much more expensive.
What else is there to do with bitcoins, other than claiming them for cash?
Here's a post that describes a ton of different ways people are using bitcoins: