I maintain several WordPress installations and always use most of the same plugins. Â I can’t ever remember which ones I need to install when I setup a new one, so this is mainly a reference for myself. Â I use some different ones here and there, but these are the main ones I use.
- Akismet
- Google Analytics for WordPress
- Lucia’s Linky Love
- OpenID
- Optimal Title
- Post-Plugin Library
- reCAPTCHA
- ShareThis
- Similar Posts
- Subscribe To Comments
- WordPress Database Backup
- WP Super Cache
- wp-cache
I would provide links to all these but as of  WP 2.7 you can just search for them by title right from within your admin panel.
I created a tool at http://www.wpkgr.com that makes this easy. Just create a custom install.php and drop in wp-content before installation. It downloads and enables the plugins for you.