Django tip: Caching and two-phased template rendering. Neat trick for expensive pages which can be mostly cached with the exception of the “logged in as” bit—run them through the template system twice, caching the intermediary generated template.
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There's also ESI for a more 'infrastructure' level solution to the problem. However support for it in caching proxies is still a little weak.
http://blog.ianbicking.org/esi-caching.html