Yesterday, Discount ASP.net launched a TFS Software as a Service offering. It’s great to have a large scale, experienced, global hoster providing hosted TFS services. Their offering starts at $20 per user per month. You can read more about it here: http://www.discountasp.net/press/2010_10_discountasp.net-launches-team-foundation-server-hosting.aspx
If you try it out, let me know about your experience.