I've been substituting a mixture of sorghum and rice extracts for malt extracts in a variety of recipes with basically good success. Beers that use either dark extract, or use dark specialty grains are more complicated, as the sorghum extract isn't particularly dark.
But otherwise, I've just been using what I think are 'good' regular extract recipes and replacing the barley malt with sorghum.
If you've got a particular style you want to try, I'm sure some of us GF brewers can help you out.