Mango includes a new feature which should increase discoverability of relevant apps immensely.
App Connect surfaces apps relevant to your search terms in the search results, for example the White and Yellow Pages app when searching for White Pages. From there it is only two more clicks before the app is installed.
Windows Phone 7.5 is expected to roll out to all Windows Phone 7 handsets over the next 4-5 weeks.
White Pages can be found in Marketplace here.