I recently purchased a Samsung SCH-u520 (US Cellular) and I am currently working to reverse engineer it for use with BitPIM  I will post my findings on this page. (using the file viewer to modify content on the phone, and hopefully developing offical BitPIM support eventually)

WARNING: All activities described in this article may result in permanent damage to your phone.  No guarantee or warranty will be offered from jmaxxz.com (and prolly not from Samsung).

Reverse engineering always carries a certain risk proceed with caution if you attempt anything described in this article.

 Getting Started:

1. Buy a usb data transfer cable for the sch-u520 
2. Download and install Samsung PC Studio (This is the easiest I found to get the required drivers, however you can not use Samsung PC Studio with this phone)
3. Install BITPIM

Adding photos:

1. Crop desired photo (must be a jpeg) to 176 x 220 pixels
2. Add cropped photo to /brew/mod/10888
3. Edit "/brew/mod/10888/Default Album.alb" (requires save to local pc to edit it then overwrite the one on the phone with the new edited one).
   Edited version should look like this (example.jpg was added to phone):
   

   0|/ff/brew/mod/10888/Default Album| ôexample.jpg|/ff/brew/mod/10888/example.jpg|0|0|3|>

Adding Music (ringtones):

1. Add music file (test with mp3's) to /brew/mod/18067
2. Edit /brew/mod/18067/MsInfo.db  to look like (example.mp3 was added):
   
   

   /ff/brew/mod/18067/example.mp3|0|5

3. Reboot phone

Retrieving Video From Phone:

1. Save .3g2 files from /brew/mod/10890 to computer from phone

Retrieving Photos From Phone:

1.  Save .jpg files from /brew/mod/10888

Locking Picture Files on Phone

1. Edit "/brew/mod/10888/Default Album.alb" 
2. On the end of each line that lists an image file there is a section like this: |0|0|3| change this part to look like |1|0|3| to make the file on that line appeared as locked on the phone. (To unlock a file change just change it from |1|0|3| back to |0|0|3|)

Text Messages:

Text messages are stored in /nvm/sms_wp_os in files with names like: sms_0045 with the exception of sms_0000

I am still analyzing the file format used in these files.