How can I find a saved Wi-Fi password? I have an Android phone which is connected to a secured Wi-Fi hotspot.  How can I find out the password of the hotspot from the phone?
On my phone, the credentials are stored in /data/wifi/bcm_supp.conf.  You'll probably need root to see it directly on your phone but you may be able to use adb pull (requires the Android SDK) from your PC to get the file.

As noted in the comments, the location may vary based on your ROM or device (specifically the Wi-Fi chip; mine's a Broadcom).  Check /data/wifi/, /data/etc/wifi/ and /data/misc/wifi/ for relevant config files if you don't find the ones suggested by eldarerathis or me.