On the HipHop Virtual Machine blog today they're announcing a new option for those that "just can't wait" to get the latest and greatest HHVM version - nightly packages.
If you just can't wait to get your hands on the latest HHVM code, but you don't want to spend the time to compile it, we have a present for you. Every midnight, we run a script that pulls whatever is in master, compiles it, does a sanity check, builds a package and sends it off to the repo. You can then use it by adding the HHVM repo normally and then installing the "hhvm-nightly" package instead of the "hhvm" package. The nightly package should work identically to the current 8 week release cycle package; it will just have all the most recent commits with much less of the testing and hardening (so beware).
The post also includes three examples of the commands to grab this nightly release (via dl.hhvm.com) and install the "hhvm-nightly" package.