+7  A: 

I love using colourlovers. Specially the palettes, since you can pick a color and get a palette with it.

Ólafur Waage
amazing, thanks.
Edward Tanguay
+1  A: 

The tools are all based on various color theories. So, it's probably best to understand that, and then the tools make more sense. There's plenty of great books on color theory.

DA
+4  A: 

I struggle with this too. What worked for me was the Colour Lovers site and especially their blog.

This site allows users to submit and vote on color pallets and, although, they could be used for anything, many tend to be perfect for websites.

Additionally, their daily blog culls out the best and also investigates interesting color trends. I hadn't thought I cared much about colors, but their site has started to turn me me around.

Michael La Voie
+2  A: 

I often use kuler, amazing product!

Colin
+2  A: 

Walk in the street, go to an art gallery, look around you, take photographs.

Great colour combinations are all around.

Colourlover blog (http://www.colourlovers.com/blog) has good examples of how real things colours can make great paletes.

Yesterday's post shows a pallete constructed out of a hotdog (Chicago dog)

Victor P
+2  A: 

This is a list of sites that I use whenever I have the 'designer's block' :)

sorry but the rules prohibited me from posting more than one 'hyperlink'...

[ Site Design/Layout ]

unmatchedstyle.com/

webcreme.com/

ffffound.com/

...............

[Interfaces]

patterntap.com/

flickr.com/photos/factoryjoe/

................

I also use most of the other sites that have been mentioned.

Dal
A: 

I find www.kuler.com to be excellent. Give it a try and let me know how you get on.

Burt