With 3.5M6, there are zipped repos for the RCP, CVS, JDT and PDE (Runtime and SDK) zipped p2 repos available with each build.
These zipped repos can be either used to provision your install or used to provision your PDE target.
Provisioning your install from a zipped repo
To provision your install, select Help->Install New Software and select Add to add a new repository
Select the archive that you have 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</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.