[wysiwtf]

The NYT has a good rent vs. buy calculator:

http://www.nytimes.com/2007/04/10/business/2007_BUYRENT_GRAP...

[nradov]

For the mathematically inclined here is another one that accounts for more factors. http://randolfe.typepad.com/randolfe/2006/04/bubblizer_a_req...