I'm not sure whether they really work yet. Let's see!
Locate a pitch on a piano keyboard with a gradually reducing margin of error. Helps to get a sense for what octave a note lies in.
Quickly discriminate between random notes and a target note. The speed aspect helps to train your absolute pitch recognition for each note, rather than relying on relative pitch skills. Try starting with a high probability of hearing the target note (e.g. 30%), then reduce it as you become accustomed to the task to increase the difficulty level.
A blind test of pitch identification ability. A series of random tones are presented and the user requested to identify each one within a short timeframe. No feedback is given until the end, where a score will be given, broken down by the individual scores for each pitch heard.
A random note generator that might help flush your short-term memory. Or interfere and make things worse?