Did you ever get the feeling that the browser address bar is the new command line? I keep forgetting how much functionality Google provides in their search text box; I was reminded when Damien Katz posted a link to a nice little Google search cheat sheet. Google also automatically recognizes certain strings, such as UPS tracking numbers, UPC codes, math calculations, etcetera. Here's a list of those shortcuts, with helpful examples. There's also a more comprehensive list of supposedly undocumented (at least on Google's web site) search operators. Interestingly, I found another list with at least one operator I've been looking for-- date range-- which doesn't appear at all on the other list:

1. link:url Shows other pages with links to that url.
   
2. related:url same as "what's related" on serps.
   
3. site:domain restricts search results to the given domain.
   
4. define:word provides a definition of the word.
   
5. allinurl: shows only pages with all terms in the url.
   
6. inurl: like allinurl, but only for the next query word.
   
7. allintitle: shows only results with terms in title.
   
8. intitle: similar to allintitle, but only for the next word. "intitle:webmasterworld google" finds only pages with webmasterworld in the title, and google anywhere on the page.
   
9. cache:url will show the Google version of the passed url.
   
10. info:url will show a page containing links to related searches, backlinks, and pages containing the url. This is the same as typing the url into the search box.
    
11. spell: will spell check your query and search for it.
    
12. stocks: will lookup the search query in a stock index.
    
13. filetype: will restrict searches to that filetype. "-filetype:doc" to remove Microsoft word files.
    
14. daterange: is supported in Julian date format only. 2452384 is an example of a Julian date.
    
15. maps: If you enter a street address, a link to Yahoo Maps and to MapBlast will be presented.
    
16. phone: enter anything that looks like a phone number to have a name and address displayed. Same is true for something that looks like an address (include a name and zip code)
    
17. site:www.somesite.net "+www.somesite.+net"
    (tells you how many pages of your site are indexed by google)
    
18. allintext: searches only within text of pages, but not in the links or page title
    
19. allinlinks: searches only within links, not text or title
    

I've always wanted to query Google for web pages created or modified earlier than a certain date, but Julian dates? Ugh! Well, at least someone already built a special Google search page to get around this limitation.