What effects will the heliosheath have on the Voyager spacecraft? I wanted to know what effects the heliosheath will have on the Voyager 1 & 2 craft. 
I know they used the slingshot method to travel through our solar system; so, with being way out in the heliosheath, how fast are the Voyagers going considering:


*

*the amount of fuel still available,

*and having no objects to slingshot around anymore? 

 A: I'm not sure what effects the heliosheath is having on the spacecraft beyond interacting with the on-board instruments which are still relaying data back to Earth.  On effect though is that there is no longer a solar wind from behind the spacecraft as they have crossed over into the transition region between space dominated by the solar wind and the interstellar medium.
As for their speed, from the offical Voyager website:

As of March 2010, Voyager 1 was at a
  distance of 16.9 billion kilometers (~
  113 AU) from the Sun.
Voyager 2 was at a distance of 13.7
  billion kilometers (~ 92 AU).
Voyager 1 is escaping the solar system
  at a speed of about 3.6 AU per year.
Voyager 2 is escaping the solar system
  at a speed of about 3.3 AU per year.

The Voyagers don't really have any fuel left, except maybe for attitude control.  (This is achieved using small propulsion-system thrusters to incessantly nudge the spacecraft back and forth within a deadband of allowed attitude error. Voyagers 1 and 2 have been doing that since 1977, and have used up a little over half their 100 kg of propellant as of April 2006 [1].)  Effectively they are just coasting out away from the solar system with the final velocities (declerated by the Sun's gravity) that they had when they left their final planetary encounter back in the 80's.
I strongly recommend checking out the web site as it has lots of great information about the on-going Voyager missions.
