Suggestions:
It is not safe nor reasonable to sample more than about 5 different wines in one setting unless you are willing to taste and spit. Since most are not willing to spit, I would suggest choosing only 5 of the guests to bring the wines, with maybe one backup, in case someone does not show up.
Change up the taste periodically. Have a blind "guess the wine type" night and give a prize. It is surprising how hard this really is.
Have a blind tasting night with a vote on best wine.
Have a night when you taste only two types of wine with 2 different brands of each, say 2 Cabs and a 2 Syrahs. Taste the Cab #1, then Syrah #1; next taste Cab #2 then Syrah #2. Use it to help people learn to recognize the differences in taste of the two varietals. (Some times it is hard to know the differences, that's why you need more than one brand of each.) Next time switch to two different varietals.
Have a night when you taste only blends.
Have a comparative tasting, where, as an example, you have a sweet wine. First you taste something very, very sweet but neutral in taste. This will overwhelm your paste buds, so that when you immediately taste the sweet wine, you will not be able to taste the sweetness in the wine. This will give each person an idea of what that particular wine would taste like if it were not sweet.
You can do the same thing with tartaric acid, oak, alcohol, tannins. For the alcohol, use plain vodka (It has almost no taste but alcohol, anyway) diluted 50% with water, so it will taste sweet, not be hot. Boil some oak chips for the oak and strain it, Mix up some tannin powder in water and strain it. It is interesting how a wine tastes if your taste buds are overwhelmed so you can't taste the acid in a wine. Same for the other ingredients. This is an easy way to determine how a particular oaked wine would taste if it were not oaked.
