Emre Sokullu over at Read/WriteWeb has written a really thoughtful, and frankly helpful guide: How To Market Your Web App . I couldn't quite get my head around the three categories Emre proposes; if a site is ready to be promoted it can get such a wide audience so rapidly surely there's never any reason to "Walk"? I'd therefore suggest there's really two categories:
Category | Character |
Walk | Mass of users does not yet make the site compelling on first visit DON'T promote yet |
Run | Mass of users already enough to make the site useful: ready to scale already |