Here's the list of Mormon-owned companies on Wikipedia. This may not be complete, but several of these are well-known, especially Bonneville Broadcasting, which has radio stations in some big markets (including 100.3 the Sound in LA, which I can get in my car here in the northern part of San Diego).

Beneficial Financial Group

Bonneville International Corporation (owns a lot of radio stations--including 100.3 the Sound in LA!)

Deseret Book

Deseret Morning News

Hawaii Reserves

Temple Square Hospitality

Zions Securities

Here's the source...

http://en.wikipedia.org/...

Deseret Management Corporation is run by top officials in the Mormon church, including the First Presidency.

Again, if one must go after the church because of Prop 8, go directly to the source--don't harm LDS members themselves (who, again, may or may not be for Prop 8--and even if they are, they may not have made an effort to get Prop 8 passed)!