I just jumped in deep on the last two WordPress projects that I’ve built getting immersed on both custom post types and custom fields, which are frequently implemented using metaboxes on the back end.
On this last project I went all out with the use of WP Alchemy metabox class for WordPress. It’s not really a plugin, it’s more of a PHP class that piggy-backs on WordPress, allowing you to create metabox fields for your pages, posts, and custom post types in the admin.
Only after I nearly completed this project did I come across Justin Taddock’s straight forward approach to metaboxes. Albeit, the WP Alchemy class has some nice additional features that I made good use of, so I think I’d still recommend it above Justin’s tutorial, but both are good reads to get you going in the right direction.