Over the last few days I've been looking at the Trafficserver, a proxy/cache/accelerator that originated with Inktomi, then passed to Yahoo, has recently been open-sourced and is now undergoing incubation at Apache. I have it running on OpenSolaris, and I expect to take a look at the API next.
Assuming it incubates successfully at Apache (and it's made a good start there), this could be a good fit for future web stack releases. Its nearest peer in the existing stack is squid. Any interest? -- Nick Kew