There is a new feature in Froyo, which when you lock and unlock the screen, a little "click" is made.
I got the idea from 17akota that this "click" can possibly be changed to whatever sound you like. The very next day, right as I was going to look for where these sounds were located, carlz28 posted where they were located.
Now, as I looked at these files, it hit me that the ringtones were the same file type, so just renamed the tone to unlock/lock.ogg, and rebooted my phone, and when I unlocked my Droid it screamed DDRRRRROIIIIIDDDDD back too me!
At this moment, I have only tested these with the ringtones in the /system/media/audio/notifications/, but I'm sure any other ringtone or tone with the .ogg ending will work too! Also, if someone can tell help me with terminal commands, I would love to post them too! But for now, I only have instructions for Root Explorer.
(This can be done with any sound in the UI sectin)
1. Open Root Explorer go into /system/media/audio/notifications/
2. Pick your desired notification sound and copy it
3. Press back once, and then press /ui
4. Press the mount r/w button in the top right corner.
4. Rename either Unlock.ogg or Lock.ogg (whichever one you are replacing) to .ogg.bak, so you can switch it back if you don't like it.
5. Paste your notification into /ui, and rename it to whichever you just renamed to .bak.
6. Close root explorer and reboot
7. Unlock/Lock your phone and enjoy!
*Note* To hear these sounds, you must go into settings>sounds> and check screen lock sounds.
Again, if someone can help me with the terminal commands, I would be greatly appreciated.
Now it is only time before themers/Rom cookers come up with sounds for their creations!
EDIT: I just tried it, and this can be done with other sounds in the UI section too! Try it out!