WordPress Themes Premium
themeforest < largest collection | from $3
mysite myway < all responsive | from $35
Theme Junkie < has a good slider theme for free called Table | support starting from $39
Misty Lake < responsive and free through WordPress
MonetizeDesign < Local Business Plugin and Local Lead Booster WordPress Theme
WordPress note, you can sort by popular
Why You Should Not Use WordPress Themes from the first page of Google results