Some time ago I read Speed reading by Tony Buzan. It was very promising so I gave it a try and for several weeks I spent daily around 1h on increasing my reading speed. It turned out to be pretty effective and I was able to read about twice as fast as at the beginning.
Short term memory training
One of the exercises in the book was for short term memory training. Basically you show yourself some number(s) for a short moment and then say it(them) out loud. Difficulty rises with shortening exposure time and lengthening the total number of displayed digits.
Check it out.