Hey,
I modified the default theme allot to match the rest of my website. In fact im the only thing the same is the PHP code. You can see the link to my blog in my sig.
The current plugins im using are:
All In One SEO - Amazing plugin, allows you to add a title, meta description and meta tags to each post and page. (Helped my first post get on page 1 of Google! for "The truth about unlimited bandwidth")
Breadcrumb NavXT - Shows a breadcrumb by copying some by pasting some PHP code to your blog where you would like it to display. A breadcrumb shows you the pages you have come from in a line. Much like on this forum where it says
Website Babble Webmaster Forums > Creating a Website > Blogging & RSS (WordPress, Blogger, TypePad, etc.) > Please Show Me Your Wordpress Blog
Sociable - Great plugin shows all the social networking links so it allows your visitors to spread the word about your blog. It also looks really clean and you can turn it off on any post/page.
Newsletter - I would say my second favourite plugin. Allows you to build a mailing list and everything is done automatically.
FeedBurner FeedSmith - Converts every feed link
www.yourwordpressblog.com/feed to any other. I use feedburner so it converted it to feeds.feedburner.com/sequencehosting
Contest Burner - A new and unique plugin that come out a couple of weeks ago. It allows you to create a run a contest on Wordpress! It records points which your visitors can get from commenting a post or promoting your website!