We ran across paid WordPress plugins now at Envato’s Code Canyon.
Some of the more interesting ones are an S3 backup tool, Cufon font custom replacement, an Ajax based WP admin login lightbox, an FAQ manager, and an internal page linker (that maybe come useless with WP 3.1 coming soon).
We’ve noticed that a handful of similar plugins can be acquired for free at WordPress.org’s plugin library.
For example, their mobile phone theme switcher ($25!) definitely has a handful of free and solid alternatives at WordPress.org. Update: The theme switcher includes 8 themes. Compare with WordPress Mobile Pack (free) and draw your own conclusions.
An advantage of buying a plugin would be if you needed almost guaranteed developer support and more detailed documentation.
Skimming through the various plugin support messages, it seems like most of the Code Canyon developers are being responsive to their customers. So if you’re on a mission critical project, this maybe a viable alternative, after all, we get what we pay for.