I've been fooling around with various hosting services on the internet and I'm getting weary of all the various limitations. Meanwhile, I've been experimenting with all the hosting technology available with Linux. I'm getting to the point where I'd like to put my own server on the internet.

How do you do that? I know that my DSL connection allows me to connect out, but not to be connected from some place else. What kind of changes, services and hardware do I need?

By the above statement I am assuming your isp prohibits hosting and therefore probably block port 80 which is commonly used for http servers. If your isp policy is to prohibit hosting then you are wise to find an isp that does. Contravening a contract by just going ahead with hosting will probably lead to you contravening your contract and having your service terminated. There are ways of circiumventing this by using other ports.
Ideally you would look for a dsl connection with static addressing as this is the easiest to configure and thereafter just install apache to host http websites and then add a mail server and php and mysl.

as long as you can set up a basic apache test page and reach it by ip address directly, then you'll be fine really, legal stuff aside.

once you've got the internal stuff sorted, all you need is a way to get to it nicely. as such, buy a domain and if you don't have a static address (or if you do too..) use a service like zoneedit.com to keep your dns details up to date. they will provide a client you can run on your machine to update their records when your ip address changes. and dns change can take hours, or even days to propagate sometimes, so a rapidly changin address ain't gonna be fun.