So, some people have been asking about memcache for Drupal 6 and my personal modules have been neglected, but meanwhile I decided to come up with something new.
Let me introduce you to Cache Router. http://drupal.org/project/cacherouter
From the project page:
"CacheRouter is a caching system for Drupal allowing you to assign individual cache tables to specific cache technology. CacheRouter also utilizes the page_fast_cache part of Drupal in order to reduce the amount of resources needed for serving pages to anonymous users."
So basically, I refactored all of the current caching strategies into a single module that allows you to mix and match. If you want page caching to use file based caching, and then everything else to use APC or Memcache. No problem. Or you can just use it to drop in memcache support for Drupal 6.
The other thing it will do is is allow "chaining" of tables, so if you have an e-commerce site, and it's critical that you use keep some custom cache table backed up to the database, you will be able to enter a backup engine that will keep your data. This is going to be done in a future version, but it is coming.
Any feedback is welcome and appreciated.