I built some Lookup formulas in XLS so that we can crunch any trade evaluations as they come up for the draft. Feel free to download it - the first tab is where you enter pick numbers to evaluate trades - tab 8 lists the picks by team (excl. compensatory picks that can't be traded).
I tried to embed the calculator in HTML and put it on a blog, but that failed.
I also have calculators for the Schuckers Model, which bases draft value on actual player performance -- 1991-2001 drafts vs. player performance through 2010 (data from pro-football focus). I also built a 'mixed model' that averages the Schuckers model with the traditional model.
Also, if you want to nerd-out on this, below is the link to Schuckers' journal paper on the subject.