An access blogger is a high-traffic blogger who makes trading on "access" -- in the classic journo sense* -- to one or several Versailles factions part of their funding and business model. OpenLeft, TPM, Kos, and FDL spring to this outsider's mind.** In the best case, you get blogs acting as "meme laundries" for talking points developed by partisan operatives; that is, they use their putative independence as a way of giving credibility to what is, in fact, a manufactured discourse that "strategists" and consultants are billing to create. (This was especially evident during the 2008 primaries.) In the worst case, you get coverage that's outright dictated by funding. (HCAN's Jason Rosenbaum at FDL was, after pressure from outraged readers, disclosed, and as an HCAN employee, it's entirely natural that Rosenbaum would censor all single payer stories in the FDL silo that Hamsher provided him. However, given lack of transparency, one must assume that there are other "cognitive infiltrators" that are not disclosed.)
Now, one can argue this is the way of the world; however, back, say, in 2003, the idea was that the blogs would replace the corrupt press, not become it.
NOTE * Much as I hate to quote Hitchens, his sad decline had not begun, or was not so evident, back in the 90s.
NOTE ** I should say that not all high traffic blogs are "access blogs" -- though funders would, naturally, like to buy them all. (The Obama 527 Formerly Known As Daily Kos has, after all, the reach of a cable channel.) Bloggers from academe (Atrios) or the entertainment industry (C&L) or the professions (TalkLeft) tend to have different, non-access based, business models. IOW, not all bloggers with access (due to high traffic) are access bloggers. They're as susceptible to a corrupt zeitgeist and manufactured talking points as anyone else, but the vector of infection is different, and their immune system is more resilient, if that makes sense. For whatever reason, the econobloggers (see Silber here) seem to be far less susceptible to infection than the political bloggers. It may be that, well, they've got money. It may also be that they simply understand the stakes better.