Now back to the original discussion.
I usually keep short/small jobs that I know my frequent members can do within 15 Minutes or less for the in-frequent members, and tend to give harder/longer jobs to the frequent/every day members.
examples of a short/small job:
-Bumper construction (1 bumper with parts already machined/Drilled)
-Assemble wheels
-Write up the weekly report for our website (If on Saturday) from our frequent documenters notes
-Have them document, take notes, pictures etc. on the days that the in-frequent PR members are in
-Design t-shirts/buttons
-Assemble buttons
-Gear box assembly if you use the regular AM toughboxes
-Clean up if i have absolutely nothing else to give them
-Assist the frequent members (All Jobs)
-Have them work on VEX (Our FRC and VEX team are the same), or our practice bot
-Assist me with field construction during the beginning of the build season
I do not give them jobs such as:
-Chassis construction/assembly
-Chairmans award video / paper
-Machining and welding (Only the frequent members are trained enough to use our mill, lathe, tig-welder etc.)
-Website
-Assemble the electrical system of the robot (1 wrong wire could be bad

)
These are only a few jobs I could think of off the top of my head.
I give them he small jobs to keep them on the team, even though they are tied up with other projects, school or sports.
Never send them home unless your rooms are filled or they are playing around, this could deter them from even coming at all.