HBO has made its first leap into broadband with a new topical comedy channel it will produce jointly with corporate sibling AOL.

“This Just In” will combine extensive video content with a blog format in a manner similar to TMZ.com, AOL’s successful year-old gossip rag, according to representatives of both companies. It will reside at ThisJustIn.com and replace AOL’s existing comedy channel at comedy.aol.com. A “Powered by HBO” tag will appear at the top of the site, which will debut in Q1 2007.

Advertising and sponsorships will be sold through AOL Media Networks, likely exclusively since HBO has never trafficked ads and does not have an internal sales organization. AOL plans to show off the new property to advertisers during next week’s HBO Comedy Festival in Las Vegas.

In a statement, AOL positioned the site launch as a first-ever opportunity for brands to associate themselves with HBO, and promised to work closely with advertisers to integrate their messages with site content.