You could do a game of Pathfinder, which is like 3.5 D&D with minor differences, a lot more stuff and also with pretty much everything you'll ever need freely available on the Internet.
I must also recommend Pathfinder. It turns a lot of people off by simply not being D&D, but it's basically D&D with the serial numbers filed off--I can personally confirm that some parts of the SRD are literally taken word-for-word from the D&D 3.5 Dungeon Master's Guide. Not only is Pathfinder Not!D&D 3.5, but it also has a ton of totally new content the 3.5 designers never dreamed of, like the Alchemist character class.
The website Harry Baldman linked is nice but also has a lot of 3rd-party crud and a huge amount of unnecessary variant rules and such, so I would recommend
the Pathfinder Reference Document instead, which is easier to navigate, offers nearly as much Paizo content, and as a plus doesn't have the often bizarre and disruptive ads on d20pfsrd.com.
You won't find out the specifics about leveling up from those sites, I believe, but if you ask around it's pretty easy to figure out.
You will need some physical things regardless of whether you play Pathfinder or D&D, though. The foremost is paper and pencils (definitely not pens!) for character sheets. You'll need some kind of board or sheet with a grid on it for battles; I made one of my own a couple years back out of the lid of a pizza box. You'll need miniatures of some sort to represent characters during fights; you can use pieces of paper with names written on them, or buy miniatures, or anything in between, really. And, of course, you'll need imagination.
Also, you'll probably have to build your own setting for this since the exact specifics of most published settings are locked away in the depths of expensive copyrighted books.