I'm in a study group right now. What we have been doing is tasting ~6-10 beers each week based on the recommended style that week. Its been a mixture of homebrew and commercial. The guy organizing it asks everyone to volunteer any homebrew if they have that style.
for example, last week was Bitters, pale ales, IPAs and IIPAs and steam beer. We tasted:
Boddingtons (Ordinary Bitter)
A homebrew ESB
2 homebrewed IPAs
1 local commercial IPA
Anchor Steam (steam beer)
1 local commercial IIPA
We officially scored 2 of the beers, and talked about a group about the rest. We also hit on how we would score all of the beers we just talked about, and why. What was good about having some homebrewed samples is that we were able to talk about what was good/bad about the beer, any off flavors (some had oxidation), and how they would improve the beer.