I am writing up a blog about Mechanical Keyboards before closing several Input.Club tabs and forgetting this great resource.
A general overview begins with learning the differences between linear switches, tactile switches, and tactile-clicky switches. Each switch type differs in construction through an extra piece being included in tactile-clicky switches, or the contact surface having a bump/angle in the case of tactile switches.
I prefer blue tactile-clicky switches which use a two part slider to produce a click sound upon depression of the key. Cherry MX Blue switches are the industry standard brand and switch, though the interest in mechanical switches has brought several competitor brands and switches.
Input Club has created graphs with measured data over many samples. This research has prompted their use of the Kaihua Blue in their new open source K-Type keyboard. The graphs and research also makes a fan of blue (tactile-clicky) switches weary of the Gateron Blue switches.