From LinnDocs

Different ways to control a DS player...

• How do I play music
• Linn GUI - Windows XP/VISTA control software
• Playlist Navigation Using Remote Control

Open Source Software check this website for any developments

• Logitech SqueezeCenter
  
• LEIA DS on Nokia N800/N810 series
• KINSKY PDA -Open Source Software - (BETA release) Software for use with a Windows PDA
  
• KINSKYGUI - (BETA release) LINNGUI for MacOSX, LINUX, WIN32 and source code
  
• Sneaky Last.FM - (BETA release) Play your Last.FM Music through the Linn DS Product
  
• Skweezy DS - (PRE- BETA release) for use with the SqueezeCentre
  

Also check the Linn Forum for any other control options

If you want to write your own software for the Linn DS products, information can be found at OSS Developer programme

Other known control applications:

iTouch/iPhone Songbook - Commercial software

iTouch.iPhone PlugPlayer - Commercial software