Three websites I now know about, thanks to the WebWatch column in the journal Biotechniques (www.biotechniques.com).
That column in the March issue contains details of an elcetron microscopy site at the Eidgenoessische Technische Hochschule Zurich, at http://www.microscopy.ethz.ch/. It has information on how the various techniques work, as well as selected images.
The same column also has details of BANMOKI, a database of bacterial nucleoside monophosphate kinases (http://www.ces.clemson.edu/compbio/databases/kinases/), and WormBook, an online review of the biology of C. elegans (http://www.wormbook.org/). This is open access and includes protocols, biology, genomics and a lot else.