I don't do it often but I have used my trailer and had 15+ bags of groceries in it it was quite full and was up to over 80 lb. or so still rode nicely.

This is what I use. That's a piece of rubber with a diamond plate design on top of the baskets. I can strap large items there without suffering major "slippage". I'm kicking around the idea of either adding a Wald basket up front, or building my own rack for the front. That's red corroplast in the bottom of the baskets.

http://img.photobucket.com/albums/v1...y192008006.jpg

my grocery gear
 

I use Detours toocan bags for normal grocery getting
http://img.photobucket.com/albums/v3...etoursbags.jpg

and for not so big stuff I use my topeak bag with fold up panniers.
http://img.photobucket.com/albums/v3.../topeakbag.jpg

If it is a big load, I use the $40 kiddie trailer.
no pic at this time