I have released version 0.2.0.1 of my reactive-banana library on hackage.
Compared to the previous version (0.1), the library has changed considerably; it now features a subset of the FRP semantics pioneered by Conal Elliott. The library contains both a model implementation that specifies the semantics and an efficient push-driven implementation which I have blogged about previously. (There are still a few inefficiencies, though, but those are easy to fix.)
The library is straightforward to use with any existing event-based framework like wxHaskell or gtk2hs; so, I invite you to venture forth and write your GUI application with functional reactive programming! A tiny sample binding to wxHaskell is provided.
The library features extensive Haddock documentation. Some example code is also provided. In the future, I hope to record in-depth documentation and tutorials, so that everyone gets a chance to learn and use functional reactive programming.