There are only so many hours in a 24-hour cycle that you can be productive -- 1/3 of which you're probably sleeping. If you can't find enough hours in the day, there is an easy way to make sleep a more productive part of your experience. Listening to audio material at night can help you memorize new information or reinforce what you've recently learned.
Memorizing While Asleep
Finding the right audio material is important for memorization while sleeping. It should be as monotone as possible and not have any loud or sudden sounds, or there's a good chance that you'll be woken up by it. Similarly, find a good audio player. If you sleep alone or have an understanding partner, a stereo with speakers would be ideal -- but an mp3 player with headphones will work too. However, it will be important to have headphones that aren't likely to fall out halfway through the night -- ear buds, for instance, aren't the most secure form of headphones.
Before you go to sleep, load the material you want to memorize into your chosen audio player and find a volume level that is audible but won't keep you up.
Set the track function to "repeat" -- repetition is key for memorization. Most audio players will allow you to repeat a track or an entire disc, which you should do for best results.
Test yourself after a few nights on the material you've been memorizing to make sure the memorization program is working. If you don't see any improvement in your recall of the material, you might try leaving the audio player at a louder volume or trying different material. Keep testing until you see an improvement in your recall skills.