There are two kinds of Freeps. (As opposed to Freepers, which are people with mullets and no common sense at all--they like Bush, for pete's sake.)
The first kind of Freep is when they attack an online poll to skew it in their favor. They like to delete cookies, reset caches, use fake e-mail addresses, whatever it takes. All thinking people know online polls are bullshit, but we are talking Freepers here.
The other kind of Freep is a meeting. They will either join in some sort of communal group hug to worship the ground Bush walks on, or they'll join to protest something. They apparently love to hang out in front of Senator Clinton's house.
This is a Freeper at a Freep...
How to recognize a Freep if you come across one: There are other pro-Bush groups and some may hold rallies. Freepers are notorious for optimistic crowd projections--as seen in pictures some DUers will undoubtedly be pleased to pull out of Freeps that had thirty portable toilets available for 32 attendees. Basically, if there's a whole slew of portosans--sometimes defended by men with rifles--and about six people to use them, that's a Freep.