DanceClone works, but if I remember right you have to convert the files or use a specific type of file. (edit: works only with mp3 not ogg) Try reading the developer's page on it.
edit: added more info from that page
You can import sm (StepMania) format step files now. Its incomplete and wont fully (or perhaps even at all) work with some files but should work with the majority of sm files. I was using “Burning Me Up” (its part of one of the contest winning song packs at www.stepmania.com though I don’t remember which one) for testing and it works perfectly with it.
from one of the wii release entries
and from the comments for the 0.3 wii version release:
May 15, 2010 at 1:57 pm
I’m glad your liking it so far
The only song I’ve tested is Burning Me Up. Its part of StepMix 1 winners pack 1.
Songs that change speeds mid song (eighth notes and things like that are totally fine but I mean songs that have multiple different BPMs) or have mid song stops (not just beats that pass without steps but parts where it actually stops) will have problems but otherwise any song should work. Any steps other then regular tap note (so hold notes or mines anything like that) will be ignored but that at least shouldn’t throw the the other steps out of sync.
Dance Clone cant actually import anything from a pack well its still in a pack though. If you download a SMZIP file then your going to need to extract the music for each individual song you want along with the actual step files (SM file) for them. I’m like 99% sure that StepMania comes with some extractor/installer that will get the songs out of the packs for you but Winrar also works perfectly fine for extracting things from SMZIP files.
Its also worth pointing out that most StepMania songs are in ogg format. At the moment dance clone only supports mp3 audio files so those will need to be converted using a computer first.
I know its all a major hassle. Improvements are going to be made.