Starting in 1988, Israel offered stamps printed on demand from vending machines. Shown here are three examples printed on a "Frama" machine. I am not sure how long these were available, but it was not a very long time. The majority of the examples I have seen have been these 3 values, but I believe others exist.
In 1990, a new version appeared, the Klussendorf machine. This machine used a colorful stamp like label, instead of the plain version used in the Frama stamps. There exist a number of paper and printing varieties of this issue. The Klussendorf report by Tari Chelouche is a great repository of information about these issues. One of the more interesting things about these issues is that the machine number that the stamp was printed from is shown on the face of the stamp. These examples are missing the machine number, indicating they came from the philatelic service machine.
Collecting these stamps offers many choices to the collector. How should these be collected? Personally, I try and get 1 stamp from each design from each machine that it was printed from. For this first definitive issue, there were 7 printings and 45 machines. Not all printings were available from all machines, but even collecting 1 stamp from each machine is a challenge. Collecting multiple values from each machine to me is a bit of overkill, and I would prefer to focus on getting one example of each. The lower value printed on the stamp, the better for me, since it means the item is more affordable.
The next issue available was of a completely different type. This is the Experimental series of computer vended postage issued in June 1991. This differed from the previous issues in that it is a self stick variety. I have seen the backing paper in different colors (Yellow and White), and printed from different machines. The mint example here was printed on machine 102056, while the used example is from machine 102058. I haven't seen these with cancels on them, since it appears they are used similar to the meter stamps are in the US, where they are applied by the postal clerk to the item to be mailed, and are considered cancelled when they are printed. There is also a variety in how the border is printed, the mint example has a T in the upper left side, while the used one does not. I also have mint examples from machine 102030, but I am not sure what other machines were used.