Sevent, a top numeric domainer, just recently started a forum for numeric domains which you should join. To kick off the forums, Sevent is selling some of his NNNN.com's for well below market value, I just got two NNNN.com's for a grand total of $375! Market price is generally more than $400 for a single NNNN.com, so this is a superb deal.
Sevent will be posting some more sales in the near future, so be sure to sign up and check the forums for these great deals. And the forum looks to be a great resource for numeric domainers to share knowledge and to conduct sales. A great development for the numeric domain community.