Coldjava (makers of the Java Servlet Office Suite -JSOS) has released v1.0 of one of the largest collections of JSP tags on the net. Their library contains 20+ tags for common programming tasks faced by JSP developers.

Tag Lib Features:
-printing formatted date/time value
-featured String manipulations
-conditional evaluation and flow-control
-generating unique ID and random values
-generating a "standard" portal view as a set of columns rom the given pages (portlets)
-page redirection
-dynamic caching of JSP content
-bar charts
-manipulations with files
-mail-reader and sendmail
-WAP/WML support

Find out more here: http://coldjava.hypermart.net/jsp.htm