"VIDEGRO's Ships" is a free Android application which allows you to receive AIS information directly from ships in your neighbourhood using a cheap (10-15 euro) DVB-T-DAB-FM / RTL-SDR receiver.

IMPORTANT: You need to have an OTG capable Android device and a DVB-T-DAB-FM / RTL-SDR receiver, otherwise this application is useless. Search eBay / DealeXtreme for 'DVB-T-DAB-FM' to obtain one.
Before buying, check the list of Supported Hardware at: http://osmocom.org/projects/sdr/wiki/rtl-sdr