Requires Perl and CPAN Module Net::DNS
The main difference to Apache's logresolve is that it doesn't fuck up with long lines containing garbage from spambots and other malware.
It caches resolved IPs in an internal hash table, so the memory consumption depends on the size of your input. You should probly run a local resolving DNS service like dnscache. It does not use multithreading or asynchronous IO to optimize speed. Patches welcome.