Take this with a grain of salt, but Public Policy Polling has posted some interesting numbers:

Our last national survey for Daily Kos found that 58% of Democrats were 'very excited' about voting this fall, compared to 54% of Republicans. Six months ago the figures were 48% of Democrats 'very excited' and Republicans at the same 54%.

Self-described teabaggers aren't as excited about voting as they were in July, a quarter of conservatives are not excited at all about voting, and African-Americans are more excited about voting than any other group of voters.