@ ranathari: Very strongly: it's my favourite textbook. There are three biochemistry books that get recommended in the first year - Stryer, Voet and Voet, and Campbell. I've never been able to find a Campbell, and I don't get on with Voet and Voet. Stryer is really easy to read, explains things clearly, and the subjects are arranged in blocks similarly to some lectures, so it's nice. A lot of the diagrams are the sort you can sketch in exams. The glossary isn't too good, but I have the Collins Dictionary of Biology as well. It comes with a CD and a website, which is always fun. Stryer, Lippard and Berg do some wonderful collaberations, and are pretty famous for having detailed, understandable and readable books. 5th edition, 2002, is massive, green, ISBN 0716746840.
@ Perfection: evil question! They aren't metallic bonds, or quite covalent, or ionic. It's like bonding in complexes, or H-bonding. The Ca is in aquous 2+, and the polar amino acids can go like a hydration shell.
(Don't ask me why they've got s instead of delta.)

Now I get to use some pics from my dissertation! Amino acids can bind metal ions in these methods:
Copyright Lippard and Berg, Principles of Bioinorganic Chemistry 1994.
The calcium in calmodulin is binding these amino acids:
Copyright Berg, Tymoczko and Stryer, Biochemistry, 2002.
You can skip the question by saying it's coordinating rather than bonding to.
Of course, the fun thing about calmodulin (CaM) is that it has four of these binding sites, and under normal conditions they're not bound! And yet, those little calciums are absolutely aching to be with the CaM! This is because Ca2+ is used as a signal in cells; for example, "Contract muscle!" incoming results in a release of Ca2+ from the places it's locked up in. The little Calciums celebrate, and go and find an apo-calmodulin (nothing bound) to bind to. When four of them bind, they activate it! And then funkyness ensues, as the CaM starts activating other stuff. Biochemistry is fun.