If you are in Philadelphia be sure to check out the Deformation Theory Seminar at Penn. Organized by Jim Stasheff, it features both young mathematicians and also seasoned veterans. Murray Gerstenhaber (a Penn professor) is a regular at this seminar. Another exciting Penn seminar is the Galois Seminar where you will find C.-L. Chai, T. Chinburg,  D. Harbater and F. Pop. This is in general a very curious audience and there are always lively conversations.