I found this at www.offshorestrategies.com and thought it was useful enough to copy here. Good thing too, it's gone from there now!

These are the outlets, not the plugs.

NEMA No.  Config  Rating 
L5-15  15A, 125V
2P, 3W 
L5-15 
5-15
15A, 125V
2P, 3W 
L6-15  15A, 250V
2P, 3W 
L7-15  15A, 277VAC
2P, 3W 
L5-20  20A, 125V
2P, 3W 
L6-20  20A, 250V
2P, 3W 
L7-20  20A, 277VAC
2P, 3W 
L8-20  20A, 480VAC
2P, 3W 
L5-30  30A, 125V
2P, 3W 
L6-30  30A, 250V
2P, 3W 
L7-30  30A, 277VAC
2P, 3W 
L8-30  30A, 480VAC
2P, 3W 
L14-20  20A, 125/250V
3P, 4W 
L15-20  20A, 250V 3ø
3P, 4W 
L16-20  20A, 480V 3ø
3P, 4W 
L14-30  30A, 125/250V
3P, 4W 
L15-30  30A, 250V 3ø
3P, 4W 
L16-30  30A, 480V 3ø
3P, 4W 
L21-20  20A, 120/
208V 3/Y
4P, 5W 
L22-20  20A, 277/
480V 3/Y
4P, 5W 
L23-20  20A, 347/
600V 3/Y
4P, 5W 
L21-30  30A, 120/
208V 3/Y
4P, 5W 
L22-30  30A, 277/
480V 3/Y
4P, 5W 
L23-30  30A, 347/
600V 3/Y
4P, 5W 
 
 
NEMA No.  Config  Rating 
1-15  15A, 125V
2P, 2W 
5-15  15A, 125V
2P, 3W 
5-20  20A, 125V
2P, 3W 
5-30  30A, 125V
2P, 3W 
5-50  50A, 125V
2P, 3W 
6-15  15A, 250V
2P, 3W 
6-20  20A, 250V
2P, 3W 
6-30  30A, 250V
2P, 3W 
6-50  50A, 250V
2P, 3W 
14-30  30A, 125/250V
3P, 4W 
14-50  50A, 125/250V
3P, 4W 
14-60  60A, 125/250V
3P, 4W 
 

IEC plugs and recepticals

The odd numbered ones are recepticals, even the plugs.
IEC numberConfig.rating (amps)
C1 & C2 0.2
C3 & C4 2.5
C5 2.5
C5 & C6 2.5
C7 & C8
(C8 not shown)
2.5
C7 polarized 2.5
C9 & C10 6
C11 & C12 10
C13 10/15
C14 10/15
C15 10/15
C15 & C16 10/15
C15-a & C16-a 10/15
C17 & C18 10/15
C19 16/20
C20 16/20
C21 & C22 16/20
C23 & C24 16/20