Note that you can still find the binaries at the old download page for now.
SigViewer is a powerful viewing application for biosignals designed to display electroencephalographic (EEG) and other biosignal data. SigViewer supports several biosignal data formats through libbiosig (for example GDF, EDF, CNT, EEG, and many more). Besides displaying biosignals, SigViewer supports creating annotations to select artifacts or specific events. SigViewer also features signal processing modules such as the average over selected epochs and the power spectrum of selected signals.
SigViewer is written in standard C++ using the cross-platform graphical user interface (GUI) toolkit Qt 4. SigViewer is available for all three major platforms (namely Windows, Mac OS X, and Linux) using one common source tree. Moreover, the application does not depend on any proprietary tools such as MATLAB or the Microsoft Foundation Classes (MFC), making it a truly free open-source program licensed under the GPL.