Every so often someone on this site (both front page writers and commenters) will mention Pro Football Focus in describing the performance of a given player. PFF attempts to provide numerical evaluations of every player in the NFL, by reviewing every piece of game tape out there. While I sometimes question their grading system, it is worth noting that they are putting in a lot of work attempting to provide us with more analysis.
We've had some back and forth on the site regarding their metrics and conclusions. If you have seen these discussions but have never had a chance to check out PFF in detail, they are offering their premium service between now and July 6 for 99 cents. The 99 cents will get you access through the end of July 6, after which you would need to pay the full price for premium stats.
If you're not sold on their grading methods but have mostly just heard about it second-hand, this provides a useful opportunity to see for yourself what they have to offer. I generally focus more on their counting stats as opposed to their analysis, but all of it at least provides another eye on things. If you have some time over the coming week, I'd recommend checking it out.