The intrepid folks over at XDA are always tinkering away to try and make using your Android device a better experience. And a few weeks ago, one of them (namely, temasek) found that the Android Market has some issues trying to resolve DNS servers when your device is connected over Wi-Fi. This can cause the Market to load slowly, and it's definitely something I've experienced on my own phone.
The solution? A popular app called Set DNS (note: root is required), which forces your phone or tablet to use a particular name server when connecting to the web, may speed up load times over Wi-Fi.