RTLSDR Scanner
A cross platform Python frequency scanning GUI for USB TV dongles, using the OsmoSDR rtl-sdr library.
In other words a cheap, simple Spectrum Analyser.
gr-scan
gr-scan is a program written in C++, and built upon GNU Radio, rtl-sdr, and the OsmoSDR Source Block. It is intended to scan a range of frequencies and print a list of discovered signals. It should work with any device that works with that block, including Realtek RTL2832U devices.
kalibrate-rtl
Kalibrate, or kal, can scan for GSM base stations in a given frequency band and can use those GSM base stations to calculate the local oscillator frequency offset.
Multimon-NG
MultimonNG a fork of multimon. It decodes a large number of digital transmission modes.