Team or partner workouts, or FGB-style time intervals for max reps, all work well. You can also combine the concepts. For example, at CrossFit DC recently we did this:
With a partner and an appropriately loaded bar, do ten rounds of power clean + push press. Maximum reps in intervals of one minute work/one minute rest, so one athlete works while the other rests, keeps score, and shouts encouragingly.
With three athletes on each bar, you could make it a 30-minute effort with one minute PC + PP, one minute pushups (or whatever), one minute rest.
Check out the CrossFit DC blog at http://crossfitdc.blogspot.com
-- Tom Brose is incredibly inventive in dealing with fairly big classes (15-20 people most Sundays) with only 1/3 as many barbells and pullup bars as we have students.