Surfing on a Brazilian website called misterwp I’ve found this huge list of websites where you can find themes for your wordpress. As the website is in Portuguese, I’m sharing this here. So if you are looking for a new design for your blog, maybe here is a good place to start! 
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WordPress Theme Viewer
WordPress templates
Hosting of High quality WP templates
Modern WordPress Themes
WordPressTheme.com
ElegantWPThemes.com
WordPress Wow Themes Gallery
WordPress Support Themes forum
WordPress Garden - Theme reviews
WordPress Theme -ThemesPack
WordPress Themes by Beng Hafner
WordPresstheme.net Free WordPress Themes
Best WordPress Themes
Free WordPress Themes - Kate's Theme Viewer
Free WordPress Themes
Free WordPress Themes on TemplateXtreme
Free beer theme by Jeremy Moseley
Blogging Pro WordPress Themes Category
Kaushal Sheth's WordPress Theme Viewer
biboz.net Free WordPress Themes
Free WordPress Themes by SiteGround
WordPress Themes by Sadish
Gii Themes
Skins/Themes for WordPress
WordPress Themes by priss
GFXedit.com Themes
Dirsurfer Themes
How to Blog's List of 980+ Themes
Alex King's WordPress Theme Competition
JohnTP's WordPress Themes Collection
Gallery for WordPress
Headsetoptions WordPress Themes
Mandarinmusing WordPress Themes
Themes for WordPress
Yvo Schapp's WordPress Theme Generator
Free WordPress Themes
miloIIIIVII
ReviewMyTheme Free WordPress Template
AllinfoDir WordPress Themes
Genuine WordPress Themes
ElegantDirectory WordPress Themes
High Quality Themes from rakCha
Aviva WordPress Themes
Deep Link Listing - Blogger - WordPress Themes
Free Sponsored Themes
Free WordPress Themes
Free WordPress Themes
BlogoSquare Free Theme downloads and reviews
Free WordPress Themes
Free High Quality WordPress Themes
Free WordPress Themes
Free WordPress Themes
Free WordPress Themes
WordPress Themes
Free WordPress Themes at CSS Design Templates
enQuira Themes
Free & Paid Themes at onehertz
Chetan Free WordPress Themes
iGuides Free WordPress Themes
Free WordPress Themes by Romow
Free WordPress Themes by blogstheme
Ext JS powered WordPress Theme
Free WordPress Themes by Yoru @ Cureless
Themes by ChiQ Montes
Free WordPress Themes
Blueverse SEO WordPress Themes
ThemeBox WordPress Themes
WordPress Themes by AskGraphics.com
Free WordPress Themes
Squeaky's - WordPress Themes and Articles
slayer's web 2.0 and AJAX Tweaked WordPress themes
Free WordPress Themes
Green Fury WordPress Theme
JTk's Free Themes
Webmaster Marty's WordPress Themes
Brétema Themes
Themeage
Best WordPress Themes
Unique WordPress Themes at wpthemez
Ericulous WordPress Themes
Professional WordPress Themes - Chromatic Sites
WordPress Theme -ThemesGallery
WordPress templates
WordPress Themed
Free WordPress Themes
Uzzz Production Themes
Balkhis WP Themes
Genuine WordPress Themes
AllinfoDir WordPress Themes
ReviewMyTheme Free WordPress Template
Rahmat's Free WordPress Themes
Gomvents' Free WordPress Themes - Updated Daily
Free Premium WordPress Themes
Dustin Hamilton Media Free WordPress Themes
Via [MISTERWP]
Have you tried iStylr.com? It lets you generate/alter your own custom wordpress template online.
Also visit http://www.smashingmagazine.com/. Tons of design tips.
Be careful. There are some reports on malicious code into theme.
Look here: http://5thirtyone.com/archives/837
hmm, thanks for sharing this
Thanks for including me in your list. It originally came from http://codex.wordpress.org/Using_Themes/Theme_List.
@nexenator: iStylr looks like something I will have to try out.
Great collection,
Thanks so much.
Cool! Peshi ischo
Thank you for this information.
Basically wished to mention Now i am thankful I stumbled onto your web site!