Everybody love Mozilla Firefox, so do hams.
1. UltraDX allows you to quickly search for Valid Ham Radio Callsigns from their extensive list of US and International Callsigns.
2. QRZ.com is one of the most popular Amateur Radio (Ham Radio) call sign database. With this search plugin you can access the QRZ.com search engine directly from your browser's search toolbar.
3. DXZone.com is one of ham's favourite site. This addon is to search any content regarding of keywords from DXZone.com.
4. HF Propagation status. Propfire displays solar/radio propagation data in your status bar. Ham Radio (aka Amateur Radio) enthusiasts and shortwave radio listeners use this to predict radio propagation.