W/ free agency, teams really don't trade much & as such, IMO "trade value" doesn't really mean much. Looked at another way, how much would a player likely contribute to another team.
Spiller .... too young/green to determine. So far, he's barely worth a roster spot.
Maybin ... lucky to make any roster.
McKelvin ... has potential to start on another team or at least would likely contribute, possibly even excel.
Lynch ... starting, but unspectacular RB.
McCargo ... doubtful he could make a roster
Losman ... lucky to make a roster
Evans ... likely starter, possibly a significant contributor
McGahee ... When we let him go, about the same as Lynch
Whitner ... see Evans Williams ... mind is drawing a blank here, so I assume not much. Wood ... he IS a solid starter
Okay, just looked it up - Mike Williams. I'd say due to lack of motivation lucky to make a roster. He HAD the talent.