Jazz and blues at a college gig? Here at Purdue, I've got the DJs I'm mentoring learning stuff off the Hot 100 charts. A lot of what's on pop radio and MTV (or MTVU) works here.
Depending upon whether you're looking to get people to just hang out or to dance all night, there are different routes to go. Purchasing the last 10 NOW CDs will help give you ideas for songs because they tend to start with dance stuff and end with chilling stuff.
Dancing stuff tends to be more of the peppier hip-hop and pop stuff (e.g. Pink, Katy Perry, Jay-Z, Lady Gaga, Britney Spears, Lil Wayne, T-Pain, Flo Rida), along with some of the peppier danceable pop/rock (e.g. Metro Station, Avril Lavigne, Boys Like Girls,).
Chilling stuff tends to be more rock heavy (e.g. All-American Rejects, Sum 41, Good Charlotte, My Chemical Romance, Fall-Out Boy, Bowling For Soup, Counting Crows) with some listenable pop (e.g. Natasha Bedingfield, Pink, Katy Perry) mixed in.
At both types of gigs, I've found that there are old classics that tend to work, like "Living on a Prayer" and "You Shook Me All Night Long" and at dance gigs, some older hip-hop and gangsta stuff tends to work. These are tracks like "California Love," "Thong Song," and "Low." However, your mileage may vary with these tunes due to regional differences.