I use hexpat and it works nicely. I wasn't able to get very far with either haxml or hxt before having grief.
HXT allows me to come close to this:
tree >>> getXPathTreesInDoc "//a"
But I haven't seen a single Haskell XML parsing library that is as nice as Nokogiri.
I haven't had to parse HTML in Haskell. I use BeautifulSoup for that. I wouldn't be surprised if the Haskell libraries aren't as useful for that kind of thing.
You might find it handy if you decide to give HXT another go :)
I am asking since it is linking to expat dynamic library..