I found this site recently that has a couple great resources you should now about. The first is a Complete GeoTrax Checklist. The list is color-coded indicating what collection the set is a part of, pictures, part numbers, descriptions and MSRP.
If you want you can get a printable copy of the GeoTrax checklist in PDF format (item picture and name only). The list is up to date including the recent Big City sets.
From the checklist page you can also link to a list of all the GeoTrax Instruction Manuals. The site is well done, it also comes with a discussion forum and some news about GeoTrax.
I do have one request...I wish the owner of the site would open the discussion forum for browsing without signing in. Search engines would have access to a lot more content that could be indexed which would only increase traffic to the site making for a larger community of contributors. Anyway, have a look and see what you think.