GR-RDS is a GNU Radio program which can be used for the decoding of FM RDS data with the RTL-SDR. It has recently been updated to support GNU Radio 3.7.
RDS is an acronym for Radio Data System, which is used in FM radio transmissions to embed information such as radio station and programme/song information. Some conventional FM radios display this information on an LCD screen.
One the authors of GR-RDS has also recently posted a video on YouTube showing it in action with an RTL-SDR source block.