Google Analytics

Woopra

GetClicky

Piwiki

Open source alternative to Google Analytics

Reinvigorate

Realtime analytics and heat sensing

Chartbeat

Realtime analytics

StatCounter

Used by Edward de Leau for farmvillechicken.com

TubeMogul

PostRank

httperf

HTTP benchmarking

See also http://www.xenoclast.org/doc/benchmark/HTTP-benchmarking-HOWTO/node6.html#SECTION00061000000000000000

TraceWatch

Free real time hit counter you install on your server (not hosted by a 3rd party)

Yahoo web analytics (aka IndexTools)

HitsLink

Hummingbird Stats