Whether they're silly (The Moron Test), useful (Instapaper), social mediacentric (Tweetie), literary (Eucalyptus), informative (SnapTell) or just plain ridiculous (iPity), apps have gone a long way to making the iPhone what it is today. The announcement that 1.5 billion apps had been downloaded came just two days after the App Store celebrated its first year anniversary, making the achievement all that much more impressive.

Apple's CEO Steve Jobs had this to say in a statement: "The App Store is like nothing the industry has ever seen before in both scale and quality." Rivals Microsoft, Research in Motion, Google, Nokia and others are said to be working on their offerings. As of this writing, however, the Palm Pre app store has a paltry 30 offerings and Microsoft's app store had yet to launch. 

With over thousands of developers and over 65,000 apps available, through an app approval process that has not been without its ups and downs, Apple has provided a model that will other companies will try desperately to emulate. Playing catch-up isn't going to be very easy.

In honor of the milestone, let us know in the comments the apps you can't live without and the apps you think deserve a wider audience.