Musician Training Center is a very interesting software environment that hosts various multimedia courses and free practice tools. I like them all, but my favorite is MET (Multilateral Ear Trainer). It is an excellent systematic and musical approach for developing intervallic ear training chops, especially optimized for guitar and bass players.
*NOTE: This is an affiliate link. This means that if you buy one of their premium courses I'll get a commission, but this is not why I have it here 😀. There are thousands of guitar products out there that I could promote, but I'm only including MTC because I consider it a valuable and effective tool for guitar players. Plus, you don't need to get the premium courses, since you can get a lot done with the free tools that they offer.