Well, Rubicon for example has 700 sell-side partners [1]... so, very large. PubMatic, I believe, is similar.
Your other options for mixing stuff in with AdSense would be to find some fairly targeted affiliate programs; however, it's tedious and requires quite a bit of upkeep.
Also a large publisher, though we've surpassed the 5k/10k thresholds without issue. Out of curiosity, though, which other networks do you use and how do they compare to Adsense?
