Here are my list of must-have WordPress plugins that make blogging much easier.
1. all-in-one-seo-pack
2. cystats
3. email-protect
4. wordpress-automatic-upgrade
5. wp-spamfree
6. Maintenance Mode
7. WordPress Database Backup (WP-DB-Backup)
You can find them and many others at http://wordpress.org/extend/plugins/
