Wordpress Mobile Edition
http://alexking.org/projects/wordpress
WP-DB-Backup
http://wordpress.org/extend/plugins/wp-db-backup
WP Ajax Edit Comments
http://raproject.com/wordpress/wp-ajax-edit-comments
CformsII
http://wordpress.org/extend/plugins/cforms
Google XML Sitemaps
http://wordpress.org/extend/plugins/google-sitemap-generator
Wordpress.com Stats
http://wordpress.org/extend/plugins/stats
Category Templates
http://codex.wordpress.org/category_templates