Ideally if one were to add a feature to perlmonks like this you would have a page that was cached and only updated when there was new data. A minimal html page is pretty cheap load-wise.

Of course... That is not a bad idea in general. I am not privy to the internal workings of the PM system but I assume every page is generated on the fly. If the server is loaded then maybe something could be implemented to write a cache page to the server only when something on that page has changed, then the script could just generate sidebar data and either read in the cache file or load it in an iframe.

Conversely if the server load is fine and it is the bandwidth that is suffering, mod_gzip could help quite a bit, if it is not being used already.