Here is a list of useful Aliens Links, if you know of any other links which you think should be included then by all means use the comment form below.
Aliens Rules by Leading Edge Games.
My Aliens Book Library.
Pendraken Miniatures do some really nice Aliens which are more than suitable.
Left picture. SFC1 Medium creature, type 1
Right picture. SFC2 Medium creature, type 2
Left picture. SFC3 Medium creature, type 3
Right picture. SFC4 Medium warrior creature
Left picture. SFC5 Small creature (10) (8mm height)
Right picture. SFC6 Queen creature (3) (20mm height)
Left picture. SFC7 Egg cluster and 5 eggs
Right picture. SFC8 Face huggers
SFC9 Face hugger victims