I think I may have posted it before, but it merits a reposting. I especially recommend these entries (mostly found on the missions, misc. page):
- Bridge to Dimension Zed (I can't believe I've been driving under this bridge for years and never once thought how weird it is that it comes from and goes to nowhere),
- Inside the Wabasha Street Bridge,
- Max Action's Crawlspace, and
- Cobb Caves.