Version 1.2.0 of the HydroAcoustic Signal Analysis System (HASAS) was released recently. If you're working on an underwater robot and need software to analyze sonar data, this might be what you're looking for. HASAS supports beam forming, direction finding, spectral analysis, transient analysis, neural network-based anaylsis, and quite a few other interesting features. Jussi Laako developed and maintains HASAS, which is free software released under the GNU GPL.