there is a newsgroup called alt.vacation.las-vegas that is chock full of this type of info. you can browse the usenet articles through google at http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&group=alt.vacation.las-vegas

However some of my favorites were

- indoor skydiving
- roller coaster tour (5-6 of them now if you count primm, jean)
- 99cent shrimp cocktail eating contest
- cinemas as orleans, palms, mgm
- m&m world
- death valley (ok not as much fun as you'd think)
- rodeo finals june 22 (not sure when they arrive)
- ethel M chocolate factory tour
- Ron Lee's world of clowns museum
- caesars omnimax

not much happening in other conventions (http://off2vegas.com/conventions/junconv.html) although they could always crash the Thompson Family Reunion

BTW - I know it will be a little hot but check out the rest of the off2vegas.com website for attractions/activities (didn't know about the cranberry factory tour).