Shimano Alfine and Nexus internal gear hubs are only offered with either twist or trigger shifters for use on mountain-type handlebars (22.2mm O.D.). To use these hubs with a drop bar requires either an aftermarket mount for the existing shifter or a replacement shifter specifically designed for use on road bars (23.8mm O.D.).
Various mounts that are intended for headlights or cyclometers can be used for adapting a stock shifter to a road bar (see examples here and here). There is also a product specifically designed for this purpose called the HubBub. The HubBub plugs in to the end of the handlebar, providing an area beyond the drop for mounting a twist shifter (the HubBub works with any twist shifter designed for a 22.2mm bar).
The J-Tek Bar-end and Versa VRS STI-style drop bar shifters are cleaner solutions than the mounts mentioned above, though they’re also more expensive. The J-Tek is a CNC machined alloy shifter similar to a Shimano bar-end. It clamps onto any standard drop bar and indexes with all of Shimano’s 8-speed internal gear hubs (there’s also a model for the 7-speed Shimano and 8-speed Sturmey Archer).
The Versa VRS-8 is an STI-style integrated brake lever/shifter designed to shift Alfine and Nexus 8-speed hubs (Versa has just released a model for the new Alfine 11 hub). For those who are accustomed to riding road bikes with integrated STI brake/shift levers, the Versa is the best (albeit the most expensive) option.
I’d be curious to hear from those who are running drop bars with internal gear hubs. What type of shifter are you using and how is it working for you?