Like everyone else has said, Ronnie's is key during the summer time. They have a great, huge patio with long picnic tables that are usually packed, not to mention all the people standing.
Beer is cheap, and they offer a lot of interesting selections that you can't get elsewhere. Inside is insanely tiny and very dark (I know, what do you expect at a bar, but it felt darker than most).
It is definitely a great place to go earlier on with a friend, or later with a bigger group. My one complaint is that there are only two washrooms. When the patio is packed with drunks on a summer night, two toilets just don't cut it.