Evolution: The Triumph of an Idea by Carl Zimmer. This is a great place to start, if you've already checked out the invaluable talkorigins website.
Life: The First Four Billion Years by Richard Fortey, who takes a very wide angle, examining not just organic evolution but also what was going on geologically and climatalogically at the same time, since everything affects the other. He's got a great "chatty" style which is pleasant to read.
Evolution: What the Fossils Say and Why it Matters by Don Prothero. So much for the fallacy of there not being any transitional fossils! This book is good because it digs deep (but not too deep for the lay person) into explaining WHY a particular fossil demonstrates evolution and how it fits into the broader play.
The Ancestor's Tale by Richard Dawkins. This one's more daunting than the previous three but an excellent read once you've got the basics under your belt. He models his tale on Chaucer's Canterbury Tales, admittedly quite loosely, but it's a fascinating trip back in time, examining retrogressively the last common ancestor before each major "break off" in homo sapien lineage.