Here's the command to check memory usage: 'ps -u macombs -o rss,command'

To reduce memory, remember to pack your Zope database via the ZMI. Then I found you need to restart Zope.

You can reduce the memory usage by reducing the size of the cache, though this may have some performance impact. In zope.conf, add a line like 'cache-size 2500'. The default is 5000.

<zodb_db main>
    # Main FileStorage database
    cache-size 500
    <filestorage>
        path $INSTANCE/var/Data.fs
    </filestorage>
    mount-point /
</zodb_db>

You can reduce the number of server threads from 4 to 3 in the zope.conf file, and reduce the pool-size:

zserver-threads 3
pool-size 3

These steps could fit your Plone 2.5.3 site into 80MB RAM.

In CacheFu, use the configuration tool to reduce the number of pages cached. The default is 500. I changed mine to 100.