CMK do a nice 1/35 truck crew of generic looking G.I.s that could easily be converted to groundcrew:
and I know Zoukei Mura are going to provide a 1/32 3 man US Navy crew loading bombs for the forthcoming 1/32 Skyraider kit, again should be no problem converting them - you can see examples painted up here:
http://scaleplasticandrail.com/kaboom/index.php/component/content/article/828
Nemrod do a USN pilot & mechanic set:
Warriors do a 1/32 Korean War groundcrew that could be converted to WWII
Evolution US Mechanics (1/35)
Signifer 1/32 US bomb loader (not a figure but hey)
Zoukei Mura also do a Luftwaffe set which you could convert to US guys:
signifer USAF starter cart WWII - Korea 1/32:
Verlinden 1/35 USAAF pilot & mechanic:
