Apologies to anyone depending on HubMed over the last couple of weeks - the server has been really slow and unresponsive. I think, hopefully, I've found the magic buttons to press, so it should be better from now on.
For reference, it's now using the my-medium.cnf that comes with MySQL (recommended for servers with 128MB RAM) and these Apache2 (prefork) settings (similar to the recommendations here):
StartServers 1
MinSpareServers 1
MaxSpareServers 5
MaxClients 8
MaxRequestsPerChild 4000