A non-exhaustive list of SDR companies for hobbyists.
Ettus Research – Ettus Research™, a National Instruments (NI) company since 2010, is the world’s leading supplier of software defined radio platforms, including the Universal Software Radio Peripheral (USRP™) family of products. The USRP B200 is one of their entry level models.
Lime Microsystems – Lime Microsystems specializes in field programmable RF (FPRF) transceivers and SDR boards for the next generation of wireless broadband systems. They product the LimeSDR and LimeSDR Mini along with the LMS7002 transceiver chip used on those boards.
RTL-SDR – RTL-SDR (RTL2832U) and software defined radio news and projects. They also sell an improved version of the basic RTL-SDR you might find on eBay. If you go this route I would purchase theirs vs a lower cost eBay option.
Airspy -Airspy is a serious alternative to both cost sensitive and higher end scanners while featuring the best radio browsing experience on the market thanks to the tight integration with the de facto standard SDR# software. The Airspy R2 is one of the SDR’s they produce.
Nuand – Makers of the bladeRF SDR initially funded on KickStarter. It uses the Lime Microsystems LMS6002D transceiver. This SDR was created a while before Lime started targeting the hobbyist market with their own SDR’s.