A few cards short of a full deck?

Left field, no ballgame.

Not the sharpest pencil in the box.

Dumber than a box of rocks.

FM ~ Definitly a colloquial Aussie term probably right across OZ. Said with a hard g (got gopher long) rather than a j sound ( flange jenny).

A pane short of a window

As thick as two short planks

Batteries not included.

You forgot -

Sausage short of a barbie

Not the full quid

Thanks lezzles how did I fergit

A snag short of a barby.

99 cents in the dollar.

See now, when I see the word "Barbie" the first thing I think is "skanky blonde doll." Which made that a very peculiar phrase, if you think about it I was trying to figure out what the hell this expression could mean and coming up with some very naughty interpretations before I remembered the barbie=barbeque thing....

http://www.able2know.com/forums/viewtopic.php?p=2250026#2250026

I can short of a candelabra

As useful as a parachute in a submarine.

Tuppence short of a shilling.

The wheel's still spinning but the hamster's dead.

One floor short of a bungalow.

A voucher short of a toaster.

She's only knitting with one needle.

His telephone's off the hook.

If brains were dynamite, he couldn't blow is hat off.

If he had another brain it would be lonely.