UMapper is a neat little tool I was sent a link to investigate. It can actually map anything into a custom map, but tweets are our focus here. I created a map for a recent conference, easily zooming into the city it was held. Surprisingly, it was fast and a great way to see what people were talking about with their avatars showing.
The engine is so powerful and I would encourage you to watch the tutorials as well as make some for your events. It is quite the hyper local tool. There is plugins for WordPress and Drupal, outside of the embedding feature. You can alway just link to a map as well.