A list of currently relevant code snapshots are available on the Google Code hosting site.
If you want to keep up with the current developments, it's advisable to track the SVN repository instead. Google has instructions for that.
If you're not using SVN yet, I'm recommending TortoiseSVN. Sean (of the Coding With The Enemy blog) recently published a series of articles on the SVN in general and TortoiseSVN in specific: Starting out with Delphi and subversion, Common tasks with Subversion, Subversion add-ins for Delphi.
After you have downloaded (and unpacked) the sources, open packages/OmniThreadLibraryPackages.groupproj, build both packages inside and install the OmniThreadLibraryDesigntime package. This will add component TOmniEventMonitor to the component palete (OmniThreadLibrary page).