First of all, when I say tradable, I don't just mean we could trade them, but also that we're likely to get "fair" value. Players who are in positions of need hold more value to us, and other teams are not likely going to value them as much as we do.
Second, everyone has picks, and most have more than us. Danford's value is less than the pick that was just used on him, which makes him pretty much untradable right now.
Minten is a recent 2nd round pick who's offensive game has not progressed (statistically) very much since being drafted. He's almost a sure-fire NHLer, but he's looking like he'll never have the offense to be a top-6er. We also have a desperate need for centers, and he's the only notable C prospect we have. Other teams just aren't going to offer the premium value we would need.
Neimela is a somewhat recent 3rd round pick who has developed well lately. He's looking like an actual future NHLer, but not a particularly high end one. He does have some value, but he's probably another year away, and won't likely ever be a top-4 guy. Also, like Minten, he's in a position of desperate need for us.
Grebyonkin, I will agree, could have some good value. We also have lots of wingers, so he's expendable.
Robertson may have some value, and he's certainly expendable. I'm just not sure how much another team would pay for him. I'm sure lots of teams would take a chance if the price was right, but nobody is paying a premium for this guy.
Woll's and McCabe's contracts are far too valuable to trade.
McMann wouldn't have much value.