What is the best all-round lens for a Sony a37 camera?

Sony Alpha SLT camera has a built-in image stabilization unlike canon or Nikon. So any lenses will do as far as your photo concern.

Personally for my a37, I use sony SAL 50mm f1.8 for portrait and 18-250mm tamron for all purpose use. These two lens are cheap enough to tempt you to buy.