Ryan, the oil ETF, OIL, tracks oil. I generally am not a long term ETF investor but have done OK moving in and out of them. I recently bought some OIL when it had a pullback so we'll see whether I am a lucky guesser.

As to Ag, I have in the past bought DBA which holds agricultural commodities. MOO and COW are two other ones. I believe MOO holds stocks like Catepillar and the fertilizers.

Below is an interesting site for energy. Kurt Wulff is very expensive as a paid subscription but he does post his picks and commentaries for the general public usually several weeks after given to his paid subscribers. When I was really into energy I checked his site weekly to see what he had to say. Site is below:

http://www.mcdep.com/