Thank you for getting back to me. I don't use any sort of PHP opcode cacher, and have seen the article you mentioned.
I already have HostnameLookups Off, and configured MaxClients and whatnot, as specified earlier. Out of the modules that I currently have enabled, are there any known 'offenders' who use a large amount of RAM? What's the primary reason that my apache2 processes would be using 50Mb of RAM so quickly after starting?