For example, here’s a partial list of what’s used on apple.com:
DoubleClick.Net Usage Statistics – Websites using DoubleClick.Net
DoubleClick enables agencies, marketers and publishers to work together successfully and profit from their digital marketing investments.
Analytics and Tracking
Omniture SiteCatalyst Usage Statistics – Websites using Omniture SiteCatalyst
Omniture SiteCatalyst® provides your website with actionable, real-time intelligence regarding online strategies and marketing initiatives.
DoubleClick Floodlight Usage Statistics – Websites using DoubleClick Floodlight
Floodlight is feature of DoubleClick ads that allows advertisers to capture and report on the actions of users who visit their website after viewing or clicking on one of the advertiser’s ads.
script.aculo.us Usage Statistics – Websites using script.aculo.us
Those wanted a more detailed look at the infrastructure behind their favorite sites might want to poke around on Todd Hoff’s High Scalability blog. Hoff talks to companies like Tumblr and Evernote about their architecture how they scale. He also tracks down information from other sources like Quora in posts like this one on Pinterest.
It looks like Hoff is using Squarespace, J2EE, YUI and Amazon S3 among other things.