MP3s and other digital sound files are all duplicated easily on the computer. Usually it is just a matter of hitting the "Duplicate" button, and you instantly have a copy of the file. One can duplicate the MP3 onto another disk if necessary. This is pretty self-explanatory and easy to do.
More recently, burning CDs has become a popular way to duplicate music. Using a CD burner and a blank CD, one can duplicate MP3s onto a new CD. One can also convert the MP3s into CD audio files before you burn so that the CD is playable on other CD players (like the one in your car). You can leave the files in MP3 format, but then you won't be able to play the CD in other players. You can also duplicate entire music CDs in one fell swoop. Click here to go to a website I created with more info about burning CDs.
Also deserving of mention are the Diamond Rio portable MP3 players (or other similar devices). One can duplicate MP3s onto the Rio and go mobile with your copied music (5).
People have been dubbing VHS tapes for a long time. Usually all that is required is two VCRs and the cables to connect them. Pop the original tape in one VCR and hit play, and put a blank tape in the other and hit record. In a little while you have a copy, albeit a slightly fuzzy one.
Dual-deck VCRs were manufactured in Asia for this express purpose. Asian nations are big on technology and don't see intellectual property in the same light as Americans do. Furthermore, they don't produce as much content as the U.S. That is why we say that Asian nations are technology-producing, and that the U.S. is content-producing. So when the dual-deck VCR was invented, it seemed like a perfectly reasonable machine to the Asian nations, one that performed a very useful and necessary function. The Western nations didn't see it that way. They tried to ban these machines from their nations, and were largely successful.
Many entrepreneurial spirits in Asia (particularly southeast Asia) frequently attempt to record movies on videotape while sitting in movie theatres. That is why you can often see human silhouettes get up to go to the bathroom when you are viewing these illicit copies. The quality of the video and audio is usually very poor, but often the price and convenience are unbeatable.
DVD (digital video disc) presents a new opportunity for duplicating movies. Since the movies on DVDs are stored in digital format, when they are duplicated there is no loss of quality. The first DVD machines to be manufactured weren't capable of recording, but many DVD recorders now exist, despite the protests of Hollywood. As the cost of recorders goes down and the availability goes up, we should see much more duping of DVDs.
Computer software has been the target of duplication for a long time. Indeed, that is one of the benefits of having a computer in the first place: you can duplicate software with the greatest of ease. The problem is when the software is copied for the purpose of distribution. A long time ago, software was duplicated onto diskettes. With the average program size much larger these days, duplicating to CD is more practical.
Video games (non-PC ones) can be duplicated as well, believe it or not. The cartridge types are very difficult to duplicate because of the uniqueness of the hardware, but those based on CDs are frequently the target of duplication. Sony Playstation games, in particular, have suffered a huge increase in duplicated games. Basically, the games are burned onto blank CDs using special software and sometimes special hardware as well (9). Playstation consoles will not play the copied games without a special "mod-chip", but this is readily available on eBay or through more illicit channels like Chipzone.com (9).