People have made wordpress plug ins for everything, but there are certain ones that every blog needs. The following plug ins are compatible with WordPress 2.6.1:

Askimet - http://akismet.com/ and use your Wordpress API key http://wordpress.com/api-keys/
aLinks - http://alinks.headzoo.com/ - Automatically links keywords
All in One SEO Pack - http://semperfiwebdesign.com/ - Add SEO techniques to your blog. Change your settings once, get the benefit each time.
cforms - http://www.deliciousdays.com/cforms-plugin
Google XML Sitemaps - http://www.arnebrachhold.de/redir/sitemap-home/
Sociable - http://yoast.com/wordpress/sociable/
SRG Clean Archives - http://www.idunzo.com/projects/clean-archives/
**Replace Smart Archives on nickswitzer.net

Subscribe to Comments - http://txfx.net/code/wordpress/subscribe-to-comments/
WWW Redirect - http://www.justinshattuck.com/wordpress-www-redirect-plugin/
WP-Cumulus - http://www.roytanck.com/2008/03/15/wp-cumulus-released
or Another Tag Cloud Program

Optional Plugins
FlickrRSS - http://eightface.com/wordpress/flickrrss/
Exec-PHP - http://bluesome.net/post/2005/08/18/50/
LinkXL - http://www.linkxl.com/wp_plugin/ - for TLA

This is just a quick little list, if you have any questions or want some advice, please contact me.