What constitutes "excellent" undergraduate research I am a junior right now and I plan on doing research over the summer and senior year. I was wondering what PhD admissions committees defined as good research experience from undergraduates in computer science?
Ok I did my studies and teaching in CS, so the following is my opinion from excellent to normal. 

Excellent: The excellent case would be achieving a research contribution, and a publication; with a help of a supervisor (and/or his/her PhD students). Also know what you want to do with your PhD (if you decided to do so).  

Good: The good case would be for you to do a research, learn how to approach reading and writing research to some extend, and now what you want to do for your PhD (if you decided to do so). 

Normal: The normal case would be the supervisor's students help you to start thinking research. In this case you will get some idea about the research and surrounding activities.