Free options: http://expressionengine.com/user_guide/general/caching.html
$70 module: http://www.solspace.com/software/detail/static_page_caching/
Notes:
- Don’t turn on template caching for an embed template that will be called several times in a loop with dynamic parameters. you will just repeat the first result.
- Tag Caching works pretty well. The only limitation is that it’s time-based.