I just thought I'd mention this. Basically, it's an up and coming medieval style RPG. It's in early alpha, but the creators are allowing free download of the game executable for people to try. You can get it here:

http://www.taleworlds.com/

There are about 10 towns in total, only one semi-built, but it's still surprisingly entertaining. It has a surprisingly in-depth combat system, with full real-time blocking and melee (you have to block with a mouse press), bows and crossbows, and even quite realistic mounted combat. Besides the mounted combat it seems rather similar to how Oblivion's combat system has been described. There's even a trade economy, if a little simple, and dozens of different weapons and armours you can purchase or find. You can have your own army and send it against an opposing army on the field. The graphics engine it uses is somewhat outdated by modern standards but it still has potential.

I've been hooked for a good 10 hours grand total I'd say. That's pretty good lastability for an alpha title! There's only a team of 3 people working on this, too.

Not to mention the game's own Construction Set is going to be released with the next patch I believe, so if you think you can do a better job than the developers, you can.

The game doesn't let you play past level 6, but for a mere $15 (£8-ish) you can play as long as you like and get in free on all the updates they do, and even the finished game. And in the process you donate towards their development costs. All in all a pretty spiffy system.

I can only second Switch's recommendation. Of course the graphics aren't awe-inspiring (pretty graphics is one of the reasons why upcoming games require so many people working on them ), neither is there content galore - but it's still very entertaining, to do a little trading here, slaughter some deserters and pirates and fight in the gladiators' arena there when there's nothing else to do.
This game does have great potential