Two wonderful and related all-girl bands that are currently active are The Softies and the All Girl Summer Fun Band. The Softies are alright - I'm not very familiar with their work - but I can highly reccomend the stuff the All Girl Summer Fun Band does (their style is pretty self-explanatory).
[The Softies: http://www.kpunk.com/softies]
[All Girl Summer Fun Band: http://agsfb.com]

Cub was another good all-girl popish rockish band, though I can't find any definitive website for them.

The Shaggs are pretty legendary - certainly not what most people would choose to listen to, but they've got an interesting story.
[The Shaggs: http://www.susanorlean.com/articles/meet_shaggs.html]

Those are four that I can think of off the top of my head, so I figured I'd contribute!