With 3.5M6, there are zipped p2 repos for the RCP, CVS, JDT and PDE (Runtime and SDK) features available with each build.
These zipped repos can be either used to provision your install or used to provision your PDE target.
These repos have a format such as
artifacts.jar content.jar plugins/ pluginA.jar pluginB.jar pluginC.jar features/ featureA.jar featureB.jar
The zipped repo is not in the format eclipse/plugins etc. so they cannot just be just unzipped over your existing install or into your dropins folder. You need to use the p2 user ui to provision them into your install or pde target.
Provisioning your install from a zipped p2 repo
To provision your install, select Help->Install New Software and select Add to add a new repository. Select Archive to point to the p2 repo archive you've downloaded from the build page.
For example, if you wish to provision from the M6 JDT source zipped repo
Select Open. You'll see the contents of the repository, identical to one on a remote http repository.
Proceed as normal to provision your install.
Provisioning your target from a zipped repo
When setting your target, select Add and select Repository or update site
Select Manage Site
Select Archive and proceed to select the zipped archive on your filesystem.
Note: Please see bug bug 268210 for issues related to provisioning from these repos for your PDE target. Currently, you can't provision from these repos in PDE because the repository browser doesn't show categories.