One option when buying a router is putting on custom firmware.
For example, you can run DD-WRT or Gargoyle, which provide features you typically do not get from stock firmware.
For example, with Gargoyle you can put quotas on individual machines (want to limit someone to 5G a month download, you can).
If you want to run custom firmware, you need to check the firmware site for what they support.
Beyond that if you are single user, buy pretty much anything.
For multi user wireless, I like dual band routers and then partition who uses what. Chuk gave some good options.
I would not touch the WRT54GL, it is a classic but is a little old/slow for the $50 price point.
When I upgraded my TV, I needed faster bandwidth to stream....when I upgraded my service, Verizon gave me a free one.
You should figure out if you are going to need to upgrade your service b/c ATT might also give you a free one.