BET Ad Network was launched in 2008. As of today, there is very little buzz about them. Its really hard to gauge if they are still active or not. When you visit the website there are no signup links for publishers, only a contact form.

Ad Groups - demographics include Black, Hispanic and Asian American consumers. They claim to have the largest reach of black consumers.

Urban Adserve
- targets the Nightlife, Professionals, Lifestyle, Youth and Family demographic.

I have never used any of these networks so I can not give an opinion. If you have history with any of these publishers, please share your experience.