Ive been working on a minecart system for my world for a day or two now, after a few attempts of making Junctions rather than having a fixed destination per track. I came up with this 4 way Junction.

When you reach it in you cart, your are stopped. You then use the lever to choose which way around the junction you wish to go, and press the button to be sent to the next stop. At this point you can either leave the junction at that destination, or stay on to pick another destination. (works from all ways entering and going around)

First real attempt at something like this, though it works for me atleast.
Feel free to use yourself, and leave feedback for me please! =D