People always ask me “What is the best plugin for Podcasting.” Originally I said Podpress, but the develop got too busy (and probably tired of working for pennies) and abandoned the plugin. I love the 1pixle player as you can change the color of the player to match the theme of your wordpress blog.
I've been a fan of Powerpress when it first came out, as they added more functionality (to tie it in with the blubrry.com network) I kind winced a bit (I loved it simplicity). However, recently updates to the powerpress plugin have made it my official plugin of choice. They added the 1 pixel player (and four others) to the mix, so customization is at your fingertips (and without a huge learning curve to figure out how). To me, this makes Powerpress, THE podcasting plugin. I still use Feedburner for my iTunes stuff, but I love the ability to have different players, and the ability to offer a download link, a streaming link, and a “Play in new window” link.
I don't use Blubrry.com for hosting (nothing against it), but they do have some great tools to make things simpler. Todd Cochrane, Angelo Mandato and the crew at blubrry deserve a round of applause for listening to their audience and over delivering on what we wanted. Check it out at http://www.blubrry.com/powerpress/
Other Plugins I Use
WordPress Automatic Upgrade is a great plugin. I know this is part of WordPress out of the box, but I like the plugin as it reminds me to back up my blog.
WordPress Autmatic Backup is a great plugin that e-mails me a backup of my blog on a weekly basis.
All in One Seo Pack is a tool that allows you to add additional meta tags, and customized titles to your blog. I like this plugin, it is easy to use, but it seems lately it needs upgraded about once a week. This is annoying. The upgrade simply takes you to the page in the plugin that asks for donations.
Tweet Meme is an interesting plugin that allows people to “retweet” your blog post. They click the button, enter their twitter information and boom, they've retweetted and put a link back to your blog (through bit.ly if you want so you can keep track).