Sleepinginairports.net is awesome! I have not slept in MSP but my mom has. I have overnighted twice in SEA, too many times to count in SLC and ATL, I've slept in DFW, DTW, DCA, LGA (horrible experience), HNL three times (actually listed myself for a flight to get back in to get in the second night one trip because I couldn't find a cheap hotel), ATH, SIN, MAD, CAE (even though I work here, I've overnighted when I've been carless), and I thought I was going to have to at BIS this week but ended up not getting there early enough to spend the night got back with the rental car 45 minutes before my flight. I've probably stayed in more but that's all I can think of off the top of my head.