You can easily host monotone anywhere you can run a daemon. With the "dumb server" support, you don't even need that -- all that is required is standard web hosting -- but this option is more experimental, and needs more work to be fully supported (want to help?).
If those two options don't work for you, here are some other options to consider:
- http://mtn-host.prjek.net provides free public monotone hosting, with an easy-to-use web management interface.
- Virtual servers quite capable of running monotone are easily available in the $15-20/month USD range -- for example mtn-host.prjek.net runs on a $20/month USD linode virtual server, currently called a "Linode 512". Similar virtual servers can be found here, here, here (this one is priced in Euros), or here (we have not used these services, and this is not a particular recommendation -- if you have recommendations, by all means add them here).
If you want to setup your own server instance, note that the monotone server can be a bit cpu and memory hungry, for example serving net.venge.monotone* takes upwards of 130 MB -- we're working on reducing this, but in the mean time, you probably don't want the very smallest servers available.