Another time and maybe day also I will put a post to links to online sites at which electronic parts can be bought, but for now:
To find information on semiconductors (Transistors, ICs, Diodes) Use the search engines from below and or just use any search engine such as Google.
To Find Semiconductors try:
And also try Google or other search engine.
To find any electronic part(s) whatsoever, use a search engine such as Google, AltaVista, Yahoo! or some other one.
Those above are mostly for finding semiconductors information.
Best way to learn how to find parts and their data is to practice with the search engines.
To get some practice enter, but only one part search at a time: