VIA C7-D 1.5 GHz L2 128KB cache with 512 MB RAM, 80G 7200RPM HD.

Basically what I am looking to do is set up a box on Slackware where I can host a fairly low traffic website, possibly with some database functionality, and the ability to use ssh and sftp to access it. It would be nice to run mail off of it as well.

Are those specs enough to do what I want? What do you think the max is that my box can handle? I might be willing to throw in a few dollars to upgrade the RAM a bit, but otherwise I am trying not to spend money.

Thanks for the advice guys.

A low traffic website with a MySQL backend and a low traffic mail server could run on there with no problems at all. In general, as long as you don't try to run game server as well, that would be a decent all purpose server.
The upgrade that would help the most without rebuilding the system would be the RAM. 2 GB would be ideal, 1GB may be within the budget range.

One of my web servers is running a 1.0GHz AMD Duron w/ 1GB RAM. It hosts several websites, about 50 users, and, looking at the logs, has served about 8000 web pages in the last 24 hours along with many, many mysql queries.

You should be fine.

note: it handled LOTS of mail just fine too, but spam assassin was a bit much for it (50 users getting 1-200 junk emails a day is a lot of spam assassin work).

I guess I might throw in for an extra 512 or 1024MG of RAM. I came up with the following in terms of running tests to see the limits of the hardware:
http://www.linuxjournal.com/article/6691
http://www.softwareqatest.com/qatweb1.html#LOAD

A lot depends on the working set size of the database. You'll be able to do a lot if everything fits into ram, and less if it starts swapping.

You should try it, starting with something simple (probably without the full database functionality) and see how it goes.