There are many sites to find new apps. I only follow iPad and iPhone/iPod so those are the ones I can recommend.
Provides detailed reviews of several apps each week.
Offers brief comments on numerous apps. There's always a section with apps that are free for a short period - often only one day - so you need to check this one often.
Great searching and sorting tools including Apps on Sale and a Watch List you create to watch for apps that go on sale.
Popular Mac magazine site with frequent app reviews
My personal blog with periodic app discussions
Numerous other sites including Computerworld, Maclife, PCworld and Datamation.