newbie questions re: memory usage, leaks and troubleshooting

["Kurt Lieber" <debian@internalcombustion.com>]

I'm running potato with Apache and MySQL and have noticed some memory
problems that I'm not sure how to troubleshoot.  Basically, available memory
keeps getting used up and not reclaimed.  Swap space doesn't seem to get
used much, if at all.  Currently, free says:

                total           used         free             shared
buffers     cached
Mem:       257952     103052     154900      32696      58040      25440
-/+ buffers/cache:      19572        238380
Swap:       658624         0           658624

But if I use top and manually add up all the values of the RSS field, I get
something around 50MB.  (BTW, does anyone know a better way to do this?)  In
fact, the values of the RSS field don't seem to match with top's summary
information at the top.  There's no single process that seems to be using a
large amount of memory, either.  ps -A v shows no single process eating over
1% of memory.

If I leave the box running for a couple days, memory usage keeps increasing
until it gets near the ceiling of total RAM.  things like Samba and apache
start to get sluggish and I end up rebooting.

I'm not sure how to start troubleshooting this, so I'm looking for some
recommendations.  I'm running a vanilla version of Potato with the only
non-stable or non-debian packages being mod_mp3 for Apache and ssh2 from
testing.  This is not a heavily-used box by any means -- it's on my home
LAN.

Thanks.