Google has recently added benchmark comparisons to Analytics. This could be extremely useful and interesting, but unfortunately is not.. well, perhaps it's just too early; this may get better as more people join.
Right now, however, the categories you can choose from are pretty limited, and worse, Google has divided them into three buckets: small. medium and large. Their explanation:
What does "sites of similar size" mean?
Based on the number of visits each site receives, sites of similar sizes are grouped together under three classifications: small, medium, and large. This way, you can compare yourself to other similarly sized sites. You are not able to view benchmarking data for sites in other size classifications.
Okay. But what's "small"? Am I "small", or "medium" and where do I fall wherever I am - near the bottom, the middle, the top? Without knowing that, I don't really know what to make of these comparisons.
And why can't I compare outside of that classification? If I'm "medium" but am near the bottom or the top of that bucket, it would seem very reasonable that I might also want to see the data from the next nearest set, right? I can't imagine that would be difficult, so it seems very arbitrary to me.
Of course this is new - I only heard about it a few weeks ago, and immediately joined: in order to compare yourself, you have to agree to anonymously share your own data. As more folks hear about this and share their Analytics data, the choices available should improve, and possibly Google will allow a bit more flexibility and provide more information about what we are really comparing against.
By the way, it turns out that "small" is really small - I have another site that gets less visits in a month than this site has every hour, but Google was able to show me comparisons for that (and it does pretty well in its category, actually). The "small" benchmark for monthly pageviews showed up as 419, so don't be afraid to join this if you were thinking your site is too tiny.