Which PHP libraries do you use?

Harry Fuecks asks – Which PHP libraries do you use?:

„For interest, wondering what PHP libraries people use? By use I mean libraries you actually trust and are willing to use / have used on a live website.“

The replies (comments) are interesting, a lot of people seem to use PHPMailer and ADOdb, and JpGraph. PEAR stuff gets used (but also rejected/criticized) a lot.