The odds for Strikeforce's Shamrock vs. Diaz main card are available at BestFightOdds.com. Here's the breakdown:
Frank Shamrock (-165) v. Nick Diaz (+145)
Benji Radach (-165) v. Scott Smith (+145)
Christiane Santos (-455) v. Hitomi Akano (+375)
Brett Rogers (-440) v. Ron Humphries (+360)
Gilbert Melendez (-315) v. Rodrigo Damm (+275)
Looking down the list of lines for this event, it's pretty evident that this isn't a card to make loads of money on, but there is a solid parlay option in Shamrock/Diaz, Radach/Smith, Melendez/Damm. It'll truly come down to who you believe will actually pull out these victories. Don't be afraid to bet multiple parlays to cover probabilities of outcomes.
Frank Shamrock (-165) v. Nick Diaz (+145): I thought there would be a bit more space between this line as Frank is likely the favorite, but this is definitely makes for some value betting for fans. Pick your pony, but I'm leaning toward Frank in this tilt. He has one of the more well-rounded games of any fighter in the sport, and unless he plays to Diaz's strengths, should be able to at least win via decision.
Benji Radach (-165) v. Scott Smith (+145): Very tough bout to call for me. I think Smith has a solid chance and pulling the upset, and I'm likely going to pick him to win it. Am I confident enough to lay down the bet on him? This may be a matchup that will be the switch bout on two parlay bets as it's a bit tough to call. Both guys swing for the knockout, but I think Radach might be more susceptible to being countered by Smith.
Gilbert Melendez (-315) v. Rodrigo Damm (+275): At -315, this is at the absolute limit for betting from me. I think Melendez wins this fight with his superior wrestling and overall tenacity, but it's not worth laying a single bet down on. I'll push the parlay.
Christiane Santos (-455) v. Hitomi Akano (+375), Brett Rogers (-440) v. Ron Humphries (+360): These lines are way too high for me. Betting way too much to win very little, and neither bout helps your parlay out at all really. The only real value is potentially Humphries if you believe he can knockout Rogers. I'm not going to risk it.
This card is really only good for one or two single bets and a couple parlays. I think Melendez is the concensus best pick to start out the parlay, and I'd push Melendez, Shamrock, and Smith/Radach. It'd almost be beneficial to see what you can payout with losing one parlay, but winning the second switched Radach/Smith fight parlay. Cover all your bases.
Diaz and Smith are solid underdog picks, and they may warrant some small bets. I will likely lay down on Smith here, but Diaz isn't going to be in this event's betting portfolio. I've seen too many poor performances from him in the past to believe he can counter Frank's well-rounded game.