The E6B circular is a clone of the CR-3 which isn't made any more.
You can do grid and convergency for one thing, time to station. The slide rule is pretty much the same with a more elegant solution for conversions.
http://www.captonline.com/CR3.jpg
As an example for convergency, say from York (roughly 54°N), you need to find a ship just East of the Isle Of Man, which is more or less on the same latitude, but 3° to the West, or 180 minutes, which at the Equator would be 180 nm. The black band represents cosines, which stop at 45°, but the cosine of 54° is the same as the sine of 36° so, looking opposite, you have 106 nm to go.
For grid, at 40W, a true track of 50 degs makes for a grid track of 90 and vice versa (just treat it like variation):
http://www.captonline.com/easagrid1.jpg