Here is a news release from JP Aerospace about their new Tandem class of dual balloon high alititude airships. (Find further details and pictures here.) :

JP Aerospace unveils a new class of near space airships.

The Tandem airship is a low cost airship capable of flight to 140,000 feet. Tandem fills the gap between free balloons and complex high altitude airships.

The Tandem does not have an outer blimp shaped shell like the Zeppelins or the Goodyear blimp. Tandems consist of two balloons separated by a keel. Each balloons is mounted on a ring. The ring can rock forward and back, but not side to side. The careful management of the low-pressure zone that exists under each balloon maintains stability of the balloons during climb. Two propellers designed for flight at 100,000 feet drive Tandems.
JP Aerospace developed the Tandem as a tool to construct the Dark Sky Station, a high altitude port and construction facility. It will also be used as a "mothership" for small experimental airships, (Mach Gliders and X-Airships).
High Racks, foam and carbon fiber balloon instrument carriers, have been the workhorse for development at JP Aerospace so far. Tandem will now step into that role.

There are three vehicles in the Tandem class. The Micro-Tandem flew on October 6, 2007. This 14 foot long airship is used as a test platform for electronics and sensors.

The Standard Tandem is 30 feet long (without balloons, 120 feet long with). The airship is undergoing an electronics upgrade. A great deal was learned from the flight of Micro-Tandem. That knowledge is being incorporated into Standard Tandem. This airship will have its first flight within a year.
Tandem Heavy Lift is 200 feet long and is lifted by roller mounted polyethylene balloons. Loads of up to five tons can be carried to 140,000 feet. Both crewed and autonomous versions are planned.

Tandems will be the highest flying airships ever built.

Tandems are short duration, low speed utilities airships. “We almost want to paint them yellow”, says John Powell, President of JP Aerospace. “Compared to the costs of other high altitude airships, Tandems are almost disposable”. As a development tool they will allow more complex upper atmospheric testing. As a construction tool they make possible large structure assemble at the edge of space.

Pictures of the airships are available at www.jpaerospace.com