If you simply want to learn the language, there is no need to look out
for professional hosting solutions. Some XQuery implementations come
with their own web server code, and they are often pretty light-weight
(and can also be run locally). As Adam indicated, if you are looking
for open source solutions, you could have a look at BaseX (disclaimer:
I’m contributing to this project), or eXist-db, which are both easy to
install, and check out the included examples.

By the way, if you only want to create xhtml pages and e.g. store them
in a file, no web server is required at all (this may be obvious
anyway).

Hope this helps,
Christian