Enzymes
The Enzymes wiki is being developed, but some great sites to go to until it is complete are:
ExploreEnz, which is a simple enzyme database based on the IUBMB enzyme list.
Expasy, which is another simple enzyme database also based on the IUBMB enzyme list.
IntEnz, which is another simple enzyme database also based on the IUBMB enzyme list.
IUBMB, which is the IUBMB website.
KEGG enzyme, which is the enzyme part of the KEGG site, a very large and useful site.
Brenda, which is a very fancy database describing details of enzymes and their pathways. Will be a real shame when this one disappears.
CAZY, which is a smaller database focused on enzymes involving carbohydrates.
ThYme, which is a smaller database focused on enzymes involving thioesters.
Orphan, which is a smaller database focused on orphan enzymes.
MMEB, which is a smaller database focused on mammalian metabolic enzymes.
MEROPS, which is a smaller database focused on peptidases.
PDB, which is a large database covering all proteins (173k structures!).
Rhea reactions, which is a large database covering biochemical reactions and the enzymes and proteins associated with them.
Worthington Enzyme Manual, which is a company sponsored database of common enzymes and proteins.
These links will probably not last long so get as much as you can from them before they disappear.