College Candy has posted some tips for stepping up your workout, New Year's Resolutions That Work. They're good tips for any time of year.
Personally, I've found that even listening to new music while working out can be a little extra motivation. I especially like listening to the White Stripes, the Raconteurs, or No Doubt (just picturing Gwen Stefani works too.)
Do you plan to step up your workout as a resolution this year?