Hardware requirements

Like most Linux-based server solutions, e-smith's hardware requirements are quite modest.

Here are the basic components you'll need:

200Mhz processor: A 500Mhz or faster processor will likely handle anything you're ever likely to throw at the server.
Basic video card: The video card and a monitor are really only necessary during installation. The same goes for a keyboard.
128MB RAM: More RAM is always better, and is more useful than a faster processor or more hard drive space.
Hard drive: Size depends on usage -- if you want to store a lot of media files on the server, a 20-40GB, or even larger hard drive is appropriate. For basic router and web serving functions, any small drive will do. Using software or hardware RAID is very nice, but it is expensive, tricky to setup, and likely overkill for a home server.
2 NICs: You only need one NIC if you are running in server-only mode, with a router handling your broadband connection. In any case, get a 100Mbps card for your internal network. The external one can be 10Mbps, since your broadband connection is likely much slower than that.
CD drive: This is also only needed for installation. You could include a CD-RW drive, but the various command-line burning tools don't seem to work that great yet. I am still experimenting with these features.

Of course, you'll also need a case and power supply, but you are more than likely recycling an older machine. If building an e-smith based home server from scratch, you might consider a small case and quiet fans.

For comparison sake, my server stats are available online.