This is a list of the plugins i use on this or other blogs:
This is the default plugin to stop spam and it is inlcuded by the default with wordpress,you only have to get a API key on wordpress.org and activate it.
Google XML Sitemaps
Generate XML-Sitemap for you blog, this is supported by Ask.com, Google, MSN Search and YAHOO
Subscribe To Comments
Allow your readers to follow comments on your blog and get an email when a new comment has been added
WordPress Database Backup
This plugin allows you to get a backup of you wordpress database on demand, or you can schedule it so you get the backup on your database in your email hourly, daily or weekly
If you want to create a photo gallery to your blog, this is a great option, it handles EXIF data, IPTC data, create thumbnails, slideshows, allows you to order photos. create albums, etc.