Search engines don't want to index pages that contain search results, because they're not useful. Most sites include entries in a special file called robots.txt that prevents search engines from indexing this kind of pages. Imagine what would happen if Google indexed its search results pages: some queries will bring the SERP as a top result.
There are some kind of searches you can find in Google:
1. Google Trends - find more than 60,000 searches, the most popular being "java, ruby, python, c#".
2. Google Blog Search - more than 687,000 searches, the most popular being "30 boxes".
3. Sketchup 3D Warehouse - more than 121,000 search pages in Google index.
4. Google Base - only 874 results with miscellaneous parameters.
5. Google Finance - although Google Finance is a content site, Google indexes pages about companies and also 32 search result pages.
6. Google PDA - Google indexes 32 search results pages from its PDA-optimized version.
7. Google Maps - more than 687,000 pages with almost no text content clutter Google index.
8. Google Music Search - more than 26,000 pages.
9. Google Books - more than 425,000 pages that contain search results from Google Book Search.
If you click one of the links above, you can add words to the query to actually search the search results.