Whew, that's tough. I solved it by sending the photos as I shot to a live Filemaker database. Decidedly NOT convenient, but way better than trying to pick through 300 people (of whom I could only personally name 50) and name them later. I had to have two assistants to make it work. It saved my butt in post, but was a pretty good juggling act during the event.
If you have the names in a list, and can identify people by face, then Aperture and iPhoto both have face recognition which works really well, but you have to individually identify a few instances of each face. It would take a couple of hours at least to run through several hundred photos.
You could probably hack a solution with an iPad and an EyeFi card. You would have to shoot in "low" resolution jpegs to make it fast, but happy snappy party photos are normally only going to the web anyway, and 6mp counts as low res these days, which is pretty darn hi-res for most people's purposes. I may try that this year, depending on how things progress technologically and business wise.