So far, the first and second one is the best one I have see yet.

• Crowd Favorite : Task Management Software | WordPress Magic | Custom Web Development
  - Seems to be one that is pretty popular and could possibly do what we have in mind.
  
• WordPress Consultants « Automattic
  - I have been looking into this one and it seem this has some really targeted developers we could use that know PHP, and very familiar with WordPress.
  
• Top 10 WordPress Plugin Developers for 2008
• ø Top 10 WordPress Plugin Developers | W-Shadow.com ø
• Covered Web Services | WordPress Consulting
  This guy is a top Developer for WordPress, I know he is $200/hour but knows his stuff.
• http://jobs.wordpress.net/

UPDATE: Some more WordPress, PHP and WordPress Plugin Developers.

• Cesarserna.com
• Jobs.Metafilter.com – this could be something that we use to get someone – I like that you put your payscale, etc.
• Scratch The Surface – 99 – Another web developer who specializes in WP Plugins. He also offers different options for making the plugins as well. Free of Charge, Pay for my time and Buy it outright.