NoSpawnChunks
What does it do?
Ever wished you could run more on less? Multiworlds taking up all your memory and noone visits them very often?
The solution is now simple: install this plugin! This plugin does one thing, and one thing only, prevents spawn chunks being loaded into memory for all worlds on the server.
What does this mean in practice?
It means you can run a 2 person server on as little as 32mb ram (including 8-10 lightweight plugins). It also means that the memory impact from having 10+ worlds enabled at once on your server is reduced to an absolute minimum.
How to install
There is no configuration, it is literally drag and drop. Just install the plugin, stop the server, and do a full restart; the plugin is now enabled, and you should notice a dramatic drop in memory footprint.
There are no known errors to using this plugin other than increased server performance ;)
Plugin conflicts
Not so much a conflict - but if you are trying to run in a low-memory situation, any plugin that force-loads chunks will ruin that for you.