Carl is right about choosing an advisor first over the college. Having said that, finding a good advisor is a hard problem. Robotics research has seen exponential growth in the last decade. One could read papers from ICRA, IROS to spot good researchers but they publish more than a 1000 papers/year each! It is very easy to get lost in the papers maze.
Here are some more options:
1) GRASP Lab @ UPenn : Deserves to be in the top 5. Works on various domains of robotics like control, motion planning, surgical robotics, AI, Learning, Vision , etc. Top researchers are Profs. Vijay Kumar, Mark Yim, Dan Koditchek, Katherine Kutchenbacher, etc.
2) University of Michigan : Michigan now has a Robotics Institute! Enough said.
3) Oregon State University : (robotics.oregonstate.edu) Their robotics efforts have grown by leaps and bounds in the past few years from having just 3-4 profs to over 10 now. Most of them are young PhD grads from CMU, Gatech, etc., who worked under the best advisers there.
4) UCSB : Look at Katie Byl, Francesco Bullo, etc.
5) Cornell University : Has big groups both in Mech and CS depts. ( Andy Ruina, Hadas Kress-Gazit, Ashutosh Saxena, etc.)
6) Harvard: Majorly into bio-robotics, multi-agent systems and allied fields. Look for Robert Wood, Robert Howe, Radhika Nagpal and Conor Walsh.
7) Yale University : Grab Lab and Scaz Lab
8) Brown : Micheal Littman, Stephanie Tellex
9) WPI : Like OSU, WPI is also very underrated.
10) Columbia : Hod Lipson, Sunil Agarwal, Peter Allen, Shree Nayar, etc
11) NorthWestern : Neuroscience and Robotics Laboratory at Northwestern University. This group is very big and well regarded in the robotics community. Also look for Brenna Argall in the ECE dept.
12) Johns Hopkins : Logically, the most comprehensive medical robotics research happens here. (LCSR)
13) Maryland, College Park: Maryland Robotics Center.
14) UIUC : Steven Lavalle - The overlord of Robotics path planning and motion planning. Need I say more? Also look at Tim Bretl's work.
There are some more at Northeastern (Robert Platt), UT Dallas ( Robert Gregg), Caltech (Aaron Ames), UT Austin (Peter Stone),etc.
Note that this list is just to help you get started. By no means is it exhaustive. I want to stress again that there are many more. Your search can only be limited by your patience and interest levels.
Try to explore these labs and figure out which aspect of robotics interests you most. I understand this could be hard for a beginner but you have to realize that robotics is vast field with a growing list of sub-domains. Ideally, a roboticist should be a jack of all trades and a master in one. So try to identify the sub-domain that you like and wish to master. This will help channelize your search and also hopefully better equip you to get started.