There are many places that offer Subversion hosting.
I think your best option is to use a cheap web host like DreamHost (*referrer link alert). Subversion is included in all their plans, which start at $8 / month or something very low like that. They also have a lot of other stuff - I use them to maintain an ISP-independent e-mail address as well.
There are also companies that offer just Subversion, but they generally cost more. Google knows of a bunch.