I recently upgraded to Ubuntu 10.10 Maverick Meerkat Alpha 64bit and as expected, the PPAs that I use have been disabled. When I enable them, I get 404 errors for most because they have not set up PPA for Maverick yet. But I need the packages, I need the updates to those packages.
To get them, all I need to do is edit them in Repositories > Other software. Here I just change maverick to lucid and then I can use and update those packages. If I later find that the maintainers have already set one up for Maverick, I can simply change lucid to maverick.
If you want to add a PPA that does not have a Maverick release, lets say deluge-team ppa which does not have packages for Maverick at the time of writing this, you can simply add ppa:deluge-team/ppa and then edit it to change maverick to lucid. That should do it.
This is not a recommended procedure but it works and has always worked for me.