I am trying to output the results of my reducer to multiple files. The data results are all contained in one file, and the rest of the results are split based on a category
You can do this in Hadoop 0.20, just that as mentioned you have to use the older API.
There's some very rough code to do so in http://github.com/orngejaket/Info_Moist_1_Splicer/tree/master/src/contrib/streaming/src/java/org/infochimps/hadoop/mapred/lib/
The resulting jar writes each record to a file named after its (sanitized) key.