GoodUI.org - Very useful read on creating great UI's. I think many apps/sites now especially those without a good designer lack a good UI though they maybe great functionally.
- Use single columns, with a clear call to action at the bottom
- Less distractions
- Guide users to call to action
- Give a gift, instead of trying to close a sale right away
- Friendly gesture
- Incentive to buy your product
- Merge similar functions
- Provide social proof - testimonials, twitter etc
- Repeat primary call to action
- eg. In a long page, have a call to action both at top and bottom
- Distinct clickable and selected item states
- Recommend something instead of just listing many choices
- Undos instead of confirmation
- Tell who its for instead of targeting everyone - "transparency builds trust"
- Be direct. "Click me" vs "Click me if you like"
- Use contrast to get attention