Akihabara48 (often shortened to AKB48) is an idol girl group produced by Akimoto Yasushi. Though their name implies they have 48 members, they started in December 2005 with only 20 girls. Currently, AKB48 has 53 members divided into 3 teams: Team A, Team K and Team B.
Right now DoCoMo mobile phone in Japan has an American Idol style commercial which features A48:
Here's a musc video for "Skirt Hirari" from 2006:
Here's a musc video for "I Wanted to Meet":
As you can see the songs are a bit sappy, it would be fun to see them do something interesting with the group like having them do kung fu on the side or battle other ninja diva mega-groups.