I have played around with Googles Custom Search Engines earlier, but now I have finally used it in a live site and it turned out quite well. On MashupSpy.com I have set up a Custom Search engine that emphazises my favourite sites about mashups – in this I have included sites about Enterprise Mashups (gartner.com), sites with lots of usefull APIs (code.google.com), sites with great tutorials (developer.yahoo.com) and sites with great mashup insipirations (programmableweb.com). See the full list of sites on mashupspy.com.
For the time it took (hours, mostly spent on learning the magics of CSS) it is an impressive functionality on MashupSpy, I will definitly use Custom Search Engines more in the future. If you have ideas on how I can improve MashupSpy or if I have missed any sites (see the full list on mashupspy.com) in my Custom Search Engine then please let me know!