Clarkconnect is a nice Soho linux distribution. I had it installed in 45 minutes. Configuring it took me about an hour. There's still a lot of work to do however, I need to install a website on it, setup easy access to postfix monitoring and fine tune the spamfilters.
For hardware I use old Compaq Deskpro small form factor workstations. They're very nice for this sort of thing since they're small, silent and don't use much electricity.
I got mine from the office where it had been sitting in a storeroom for some years. I had two old maxtor disks, a 40 and a 30gb and 384mb of pc133 ram. Fitting two disks into this tiny case seemed a challenge at first untill I decided I didn't need the floppy drive anyway.
During install the clarkconnect installer suggested combining the two disks in one file system so now I have 70gb of storage.
Mine didn't have a cdrom player which wasn't too much of a problem since I only need it during installation, just a matter of hooking up a normal cdrom player temporarily with the case open. I could have installed one of course but these machines take those slimline players and they're expensive and hard to find.
You can often find these machines or simular ones from Dell or HP in shops that sell batches of old company equipment, in this country a nice one will set you back about 70 euros. If you do shop around for a machine like this try to find one with a lot of memory. They often have only two SDRAM sockets. PC133 RAM is still around but new it's very expensive. On ebay you can expect to pay around 25 euro for 256mb and prices are going up. Clarkconnect will run on 128mb but runs a lot better on 256mb. With Ram it's just like money, it's difficult to have too much.
I realize that a 500mhz CPU and 384mb of memory doesn't sound like a lot in this age of multiple Ghz CPUs and multiple Gb memory but it's quite sufficient to run a fileserver, webserver and low volume mailserver. I'll post some load statistics later on.
If you are running a server don't forget to enable port forwarding on your ADSL modem (or whatever you use to connect). Here's a guide for the Alcatel Speedtouch modems that are extremly common in the Netherlands.