I think at this point the question has to be: "what should we do to create a playoff team for 2009/2010 and beyond?" The chance that the Sens can recover this year is just too low right now to worry about the second half of the season.
So I think the challenge has to be to identify the players who could be playing for that future playoff team. Or, which players are not really going to be contributing in a year or two and are denying playing time to the guys who might get good.
The problem players are McAmmond, Donovan and Ruutu. It's not that these guys are having bad years; in fact, all of these guys have pretty good +/- numbers, at least compared to some of the players. The problem is that once the Senators improve, these three guys will not be key members of the team. They're basically fill-in players, the kind of guys you can pick up pretty easily. When you're a top five team, it's always useful to have guys like this around. But right now, they're just taking time away from young players. The Senators need to be using a lot more young players right now, because in a year or two some of them might get really good. Yes, there is a risk that the team gets even worse this year, but at this point I would take that risk in exchange for a better team in 2010/2011.
So I would entertain offers for the three players above, and take draft picks or prospects. The one other problem player is Vermette. He's a bit different, because his age (26) and his past performance suggest that he might recover over the next few years. If they can get a good package for him, take it; otherwise, I guess you keep playing him and hope for improvement. I don't know what his contract status is.