sigTOOL is a general-purpose signal processing package that runs in the MATLAB environment. It is open-source and free-of-charge.
Built-in analyses are currently targeted at those working in electrophysiology and neuroscience. If you are working in these fields, sigTOOL's extensive file import facilitities probably already support your data format (e.g. from Alpha Omega, Axon Instruments, Blackrock Microsystems, Cambridge Electronic Design, Heka, MultiChannel Systems, NeuroExplorer, NeuroShare native, Plexon and other software).
If you want simply to analyse your data:
sigTOOL provides an intuitive graphical-user interface based program for analysing waveforms and spike-trains. This provides menu-driven analysis, plotting and data export facilities using the underlying sigTOOL environment. Features supported include: spike-train analysis (PSTH, JPSTH, rasters, ISIH etc), spike recognition, waveform analysis (digital filtering, resampling, correlation etc) for both continuous waveforms and episodic data (e.g. local field and evoked potentials).
If you are a code developer:
sigTOOL is a code development environment that is built on top of MATLAB to help with writing custom software in signal analysis. You get the full facilities and power of the MATLAB environment together with the convenience of easy-to-use data access, plotting and export functions via sigTOOL. Essentially, sigTOOL let's you write and re-distribute original code without re-inventing the wheel. Code developed with sigTOOL will automatically slot into the GUI and can be zipped, redistributed and used in any lab using a sigTOOL-supported file format.