Hey guys, I've seen WAY too many threads for this problem. I thought that rather than responding a billion times to threads with my opinions and results of research, I'd just make an official thread.
Post ANYTHING that you may find, or post that you have the problem here.
What is the problem?
The problem is that after us Droid users have been using our headphones, there is no sound through the built-in speaker after unplugging the headphones. Using headphones again does work. Essentially the Droid is stuck in Headphone mode.
What has been found out?
Through my extensive research (this is my mp3 player)
I've concluded that it is a software problem. I have not taken an extensive look into the software, but experimentation has proved otherwise.
I can use my headphones for about 3 minutes and still be able to use the speaker after unplugging them.
Also, if you look at the top of your droid at the headphone jack, it's possible to push it in, showing some play. This contributes to the cracking headphone noise problem, and needs to be remedied somehow. How, I have no idea. We'll leave Motorola Engineers up to that.
The problem of the loose headphone jack could also have to do with the no sound after headphone problem. There are terminals inside of the device that could possible get bridged or spark, which would essentially cause the phone to be in a continuous cycle of thinking there is headphones plugged in.
To fix the phone temporarily, restart it. Long hold of power and click Power Off.
I've also found out that it is possible for the phone to think that there were/are headphones plugged in, while it is entirely impossible (didn't use headphones at all)
If you try the method below and it doesn't work, try taking a pair of headphones, inserting them in, then slowly pulling on the connector. This will cause the port/receptacle for headphones on the phone to be pulled out, and after a restart, should cause the phone to allow use of the speaker again.