One easy and fast method to convert WMA to Ogg Vorbis is to use the dir2ogg script included in the repositories. To install it, type as root:
apt-get install dir2ogg
Then use it like:
Or, if you have several WMA files in a directory:
Notice that it is not a good idea to convert lossy WMA audio to Ogg since the quality will degrade, it's better to use this on WMA lossless only.