For me the best place to look for datasheets for jelly-bean components - is http://www.datasheetcatalog.com/
Not google, because in datasheetcatalog you can select datasheets from different manufacturers for a given component.
Usually when searching for components I use two websites: http://DigiKey.com/
(o, well, and google of course)
But I wanted to tell you about one thing that _really_ speeds up searching for datasheets.
It's a small browser tweak I use - search engines keywords.
For example: If I want to look for BC817 datasheet, I just type "d BC817" (without "", of course) in my browser address bar. And momentarily I'm getting list of datasheets from different manufacturers for BC817 from datasheetcatalog.
The same way I can search for videos on youtube typing: "y SomeVideoNameToLookFor" or on wikipedia "w nuclear reaction", etc.
To add DatasheetCatalog to the list of search engines I've used "Add To Search Bar 2.0" firefox addon (which you can find in list of official addons).
I've included some screenshots - they're pretty much self-explaining.