Check out http://www.bocacom.net. They offer Windows 2003 servers with 500 GB transfer from about $99.00 a month. Servers are all Dell Poweredge Servers. Very reliable and prompt support/service. I highly recommend them.
I sencod iTec Hosts, you should give bocacom a try, they offer some nice Windows 2003 web edition and Windows 2003 standard edition servers... they have all the range, from Celeron 1.8 to Dual Xeon 2.4.
What is the most you are looking to spend on a server per month? What specs are you looking for? Celeron? P-4? AMD? How much ram?
The answers to the above questions will allow us to provide you with answers keyed to what you are looking for.
So far, the leading dedicated server providers (ev1servers, servermatrix, bocacom) have all been mentioned. They are all close in price and features. Although I feel Bocacom blows away ev1servers for support.