We have
http://ridewithgps.com hosted on our own co-located server with
http://colostore.com for $50 a month. It's a 2U server with dual 700w power supplies, setup on two separate breakers. Server was setup within 4 hours of UPS dropping it off last December, and we haven't experienced any downtime or network issues.
Colostore is the best Zack or I have found so far, however, they are not the people to use if you require much help or a managed solution. Also, it looks like they have jumped up the price of co-location since then to $70 a month, which is still pretty good for the level of service they offer (2TB a month, 5 IP addresses). I would still happily pay that amount for their service.