Bazaar nightly Ubuntu packages are available from ppa:bzr/daily. The old ppa, ppa:bzr-nightly-ppa/ppa was out of date and has just been deleted.
To get nightly bzr builds on Ubuntu, say:
sudo add-apt-repository ppa:bzr/daily
sudo apt-get update
sudo apt-get install bzr
and as of today you should get a 2.4 beta snapshot.
maxb has built packages of bzr-svn and its dependencies into
ppa:bzr/proposed, including a new and much better version of the Subvertpy subversion bindings. He is looking for positive or negative test results from people using these on Ubuntu hardy and jaunty. If you do use bzr-svn on those OS releases, please give them a try, or at least Max know (here or on the list) that you care about getting updates…