[Joel]

Originally Posted by antwerpen

I'm pretty new to Omnigraffle and was hoping to use it for this. However I have so far found it extremely frustrating since lines only snap to the middle of objects and can't be drawn freeform. If anyone knows how to keep it from doing this, please let me know.

Hold down the Option key while drawing a line and it won't connect to anything. Similarly, you can inspect the Line Tool and by using the Connections Inspector have all lines not connect to any other objects.