I do not do a lot of PPC and so I am curious how often do people who spend thousands of dollars in PPC test their landing pages? How often do you get new landing pages designed? How much testing do you do on conversions from various designs?
User Testing.com (see above) does a great job in explaining a relatively new concept. You know exactly what they offer: for $39, you get a video of a visitor speaking their thoughts as they use your website.