Web Performance Tools

Firebug
YSlow
Page Speed
Speed Tracer (Chrome)
HttpWatch
DynaTrace's Ajax Edition
webpagetest
Web Inspector
Chrome Dev Tools
fiddler2
HttpAnalyzer
IE Developer Toolbar

yuiCompressor
http://csssprites.com/
SpriteMe
jawr.java.net
Cuzillion
OctaGate SiteTimer

JSMin
AlertSite Dejaclick recorder
cuzillion (steve sounders)
Doloto from Microsoft
www.csssprites.com
spritegen.website-performance.org
pngcrush (optipgn, pngoptimizer, gifsicle)
jpgetran
imagemagick
png2ico
AOL pagetest
IMB Page Detailer
LiveHttpHeader
JSLint
JDrop