In terms of CS, University of Colorado, Boulder (http://www.cs.colorado.edu/) is a great school. It's not Cornell, MIT, CMU, etc (Posterous favourite school..) but definitely top 10-20 depending on sub area.
I also like Colorado School of Mines (www.mines.edu), but not sure they're in Boulder.
Colorado School of Mines is in Golden, CO. It's about a 45 minute drive from Boulder.
I did my undergrad there, and the CS department is very good. For grad school it really matters what area you are specializing in. CU is really highly ranked in some areas, and doesn't have any profs focusing on other areas of CS.