Microsoft Activesync allows you to sync only one Files folder from your desktop PC (located under My Documents) to your Windows Mobile device. Easy Sync is a free software that allows you to sync multiple folders from your desktop to your Windows Mobile device including external Storage Cards. This software supports three types of synchronization:

Synchronize - files are two-way copied until the content of linked folders is equal.
Copy/Move to Desktop - all files from pocket folder are copied / moved to the desktop folder linked with the pocket one. Files in the desktop folder are left without changes.
Copy/Move to Pocket - all files from desktop folder are copied / moved to the pocket folder linked with the desktop one. Files in the pocket folder are left without changes