First week of Plugin Weekly, and it’s a good one:
WP Super Cache – Everyone should have a copy of this plugin. It’s basically a very fast caching module for WordPress, and essential for when one of you’re posts gets made popular on Digg, or starts getting a lot of hits.
WP Polls – This plugin adds an AJAX poll system to your WordPress blog. You can easily include a poll into your WordPress’s blog post/page, and it’s very customizable.
obsocialbookmarker – Adds user-submission links at the bottom of each post for various social bookmarking sites which allows your visitors to easily submit them in a number of social bookmarking sites. Includes: del.icio.us, reddit, slashdot it, digg, facebook, technorati, google, stumble, and a lot more.
Also, check out MtDewVirus for a collection of over 10 plugins that are small but quite handy.