I have had very good experience so far with grainhedge.com. Their commission is about $15 $17ish a complete in and out futures trade. I have not tried trading any options through their site. If I needed to talk to somebody on the phone they have been very easy to get a hold of. You do have to pay a subscription for their trading platform if you want to use it. Otherwise you can make simple trades through the website w/out a subscription.

TD Ameritrade is also very cheap, but they are weak on their ag futures offerings. No mini contracts, no KC wheat, etc. Just basic corn, soy, wheat, livestock.  But their platform Think or Swim is free, and I do like it.  

Whatever you decide to use, figure on about 2 weeks getting everything setup and approved. Takes a whole stack of forms and disclosures to open a full on futures account.