The Administrative Appeals Office (AAO) of the US Citizenship and Immigration Services has appellate jurisdiction over approximately 50 different immigration case types, including most most employment based visa petitions. See the Executive Office of Immigration Review page of this guide for other agency decisions.
Westlaw has Interpreter Releases which provide weekly summaries of immigration court decisions. They go back to 1987.
Westlaw also has the following immigration agency decisions:
Non-Precedent Decisions from Administrative Appeals Office (AAO) from February 1985.
Precedent Decisions AAU/AAO go back to 1940.
Agency decisions on the internet: