Don't do this. Go to a commercial web host. If you just want to fiddle, sure go ahead and set up a webserver on your Lion server and use it locally. If you want to fiddle, and want the result on the public Internet, get a cheap VPS.
If you really insist: it's going to suck for your users, because you almost certainly have limited outbound bandwidth from your ISP. They also likely prohibit this usage of their service, and you could get in trouble if they find out. It's also likely that they just block port 80 inbound.
If your ISP DOES allow it (unlikely) and they DON'T block port 80 (unlikely) you still have to deal with the fact that you probably have a dynamic IP address. You'll need to set-up forwarding with a service like dyndns.org. Not a big deal, and you can do it for free, but the result is still going to suck.
You will also have to set-up your router to do "port forwarding" of port 80 to your server.
Web hosts belong in a data center. Period.
Oh god, these people. I'm going to be an Apple Certified System Administrator in a week and I would never use a data center unless I required huge amounts of bandwidth, cooling, etc. In other words, a service that supports many people downloading video simultaneously. I'm supporting all of my iOS apps, mail, MySQL databases, contacts, calendar, OD, websites, files, and VPN on a 27" iMac running Snow Leopard Server in my office. If you're ever looking to set money on fire for no reason... go data centers!!
If your ISP is blocking port 80, try hosting your site temporarily on another, higher up port (above 1000) and then try to access your IP address in a web browser (e.g. http://IPAddress:8080).
Additionally, try testing to see if your ISP allows inbound requests over port 80 by going to canyouseeme.org. Another popular port to block is port 25, used for mail.
I agree 100%.
I'm just explaining WHY ISPs have the restrictions that they do. It's NOT "fear of the unknown."
I provided the OP with a likely solution: run his personal website on a port other than port 80. I suspect that his ISP is blocking port 80 inbound, and there's nothing he can do about it.
He can set-up his site on a port other than port 80. Users will have to add the port number to the URL. Obviously, this would not be acceptable for a commercial site, and that's exactly why ISPs do that.
BTW, he did say "nothing big RIGHT NOW." Sounds like he hope to run a "real" website in the future. If he wants to fiddle and learn, I'd suggest that at some point he start doing that in the environment in which he will have to operate when/if he has something that will draw significant traffic.