The merges for Firefox 6 onto the Beta Channel, Firefox 7 onto the Aurora Channel as well as Firefox 8 onto the nightly channel has been completed. You can move to the next version within your channel (Firefox 6 Aurora to Firefox 7 Aurora) by going to Help > About Firefox (or Aurora or Nightly). If you want to update manually you can get the builds here:
- Nightly (Firefox 8.0a1)
- Aurora (Firefox 7.0a2)
- Beta (Firefox 6.0b1) Mobile Version available here as well