Call to Action Buttons - Examples and Best Practices

As usual the trick is to get inspired and not slavishly follow any particular implementation. Due to each site having differences in design and purpose, the only way is to do continuous a/b testing.<p><a href="http://visualwebsiteoptimizer.com/split-testing-blog/tag/call-to-action/" rel="nofollow">http://visualwebsiteoptimizer.com/split-testing-blog/tag/cal...</a><p><a href="http://www.campaignmonitor.com/blog/post/3073/a-b-testing-the-difference-one-line-can-make/" rel="nofollow">http://www.campaignmonitor.com/blog/post/3073/a-b-testing-th...</a><p><a href="http://thinkvitamin.com/web-apps/how-to-increase-sign-ups-by-200-percent/" rel="nofollow">http://thinkvitamin.com/web-apps/how-to-increase-sign-ups-by...</a>

I'm amazed at the amount of "this is crap because I already knew it" comments in the articles comment section. Sure one sees this a lot on the web but it seems to me that it's becoming more and more common.<p>As a hobbyist in the field I find articles like these very interesting. However I find it hard to find larger collections, or even better books on such subjects. So much of what I come across is bloated with crap. Very seldom can I find collection focusing only on the why and how. Any tips?

See also: A Quick Web Design Case Study - Apple Macbook Air Call to Action<p><a href="http://voltagecreative.com/articles/web-design-case-study-apple-macbook-air-call-to-action/" rel="nofollow">http://voltagecreative.com/articles/web-design-case-study-ap...</a>

Anyone doing A/B testing of buttons have a color recommendation?