Don't bother trying to get lucky on the 50BTC block bounty; join a pool that splits the winnings. Pools provide well over half the calculation capacity of the Bitcoin system, most are free to join and ones worth joining don't have any real requirements.
I make about 1 BTC per day just with spare GPU cycles on my desktop; it's not a substantial amount by any means, just a test pool for experiments and playing with software.
AFAICS, the benefit to being in a mining pool is you can make some bitcoins immediately, rather than waiting for a big, rare payout. There's no increased probability of winning due to pooling resources is there?
There is an increase of about 1% if the pool uses long polling. Pools are more well connected and notify your client, when block changes (without this you can work on an old block for some time before you get notification from the network).
There is a small increase in probability because the pool is aware of the participants and thus reduces redundant work done by each participant. It becomes a slightly-less-than-random brute force operation.
If you mine on your own, then your targets are effectively random.
I make about 1 BTC per day just with spare GPU cycles on my desktop; it's not a substantial amount by any means, just a test pool for experiments and playing with software.