Peer1 is a large Canadian datacenter & network provider; with datacenters on both coasts and both in USA and Canada. The new Stack Overflow server farm is AFAIK hosted in Peer1's New York DC, and Peer1 has hosted Joel on Software for years.
One little thing: last I heard about Peer1 the word was that most of their DCs are occupied at or near capacity, so they're not exactly hungry for new customers. This may or may not be true. It was a while ago that I heard this, and it was anecdotal evidence only.
Edit: I see that Peer1 has a new DC in Toronto, so they ought to be hungry for attracting customers to that DC.
Price is a factor but it has to be a tier 1 provider needed for financial companies and their data. They may need to be certified per financial industry requirements such as SAS 70 etc.
Cheap or certified -- pick one.
Lastly, I keep saying that this site isn't really the best forum for ISP and Colo recommendations. Try Web Hosting Talk's forums, or maybe some of the other Stack Overflow network sites.