pcAudioLabs is a one-stop shop for anything related to computer-based music production.
They sell music software for synthesis, sequencing, recording, and mastering. They sell computers optimized for music production, along with audio peripherals such as MIDI interfaces, keyboards and controllers, and audio interfaces. If you’re learning computer music, they carry computer-based music tutorials.
One of the best aspects of the site is an active user forum. The pcAudioLabs forum is an excellent source of information on computer-based audio workstations.