I'm looking into this as well. I've just got a G4 tower up and running which was given to me by a friend after they followed my example and got a Mac Mini, and me and my dad are working on using it as a live web-server to host our own personal site on. We were Windows guys in the past, but switched to OSX and haven't looked back, that said we're still relatively basic in our understanding of the more advanced stuff in OSX.
Basically, what we'd ultimately like is a server that could run full time (I looked into some stuff like MAMP and it said it wasn't suitable for live servers, but only as a development environment, which got me worried about taking this idea any further using it) and what we want functionality wise is stuff like:
-Basic front page (of course....)
-File/media hosting capabilities (to download and upload, media playing facilities would be nice but not essential)
-PHP/MySQL/PHPMyAdmin (basically I love messing around with forums and stuff, mostly SMF, and I want the ability to host a forum as part of this site as well)
Now I have literally no idea how to go about this, I've looked over quite a few guides on the net, quite a few after searching for 'OSX as a server' before I realised what we actually wanted was a web-server, which seems to take more steps. I've also seen most of the links on this thread already on my travels. I think I could probably get it running fine as a basic webpage and my dad would be happy enough, but ultimately the PHP/MySQL support is something I'm really keen on as I'm determined to get my own forum hosted and working in house. Therefore I was wondering if anyone knew how I should go about this literally from start to finish, as I've found how to turn it into a web-server, but info on the PHP/MySQL is kind of sparse and I can't really find out how to add this functionality on the end of the guides I've found, or even if I'd need to perform any extra steps in the basic web-server set up. Can anyone help with some pointers, or even a full guide on how I'd get to where I want to be?
Oh, and by the way we're kinda cheap.... Free is obviously preferable where any extra software is required, but we'd be quite willing to shell out something reasonable if it helped us along, we were just put off by the $499 price tag on OSX Server.