The IRS published their new procedures for filing 1099 electronically for tax year 2007.  This is normally documented in IRS Publication 1220, but you can find the same information in IRB 2007-30. [html] [pdf]

If you new filing 1099s electronically, wikipedia has a decent article to get you up to speed.


*UPDATE* 29 AUG 2007

IRS has published an updated version of IRS Publication 1220, which covers electronic filing of 1099s for tax year 2007. [IRS PDF Download site]