Ser más listo que el hambre

[ROBINDESBOIS]

English?

[EmpanadaRica]

My (non-native) two cents:;)

Perhaps:

'Sharp as a needle'
'He/ she is one smart cookie' (more usual for women maybe?)
'Smart as a whip'

smart as a whip - having or marked by unusual and impressive intelligence; "some men dislike brainy women"; "a brilliant mind"; "a brilliant solution to the problem"

http://www.thefreedictionary.com/smart+as+a+whip

[Rusty]

All good contributions, EmpanadaRica.

Here's another:
To be as smart as they come

[poli]

I hear "sharp as a tack " and never "sharp as a needle", but these terms may be regional.