Magic Set Editor (shortened to MSE) is a popular program among custom card creators, which is used to render Magic cards with pre-made templates; its popularity is attributed to the program's relative ease of use, user-friendliness, flexibility, and decent-quality product.
The author of MSE is Twan van Laarhoven, who is registered on the MTGS forums as twanvl, and the most current version is 2.0, released on February 5, 2011. The other members of the current development team are Coppro, Pichoro, art_freak, and Idle Muse.
Expansion of MSE
MSE has expanded out to other games, including Vs. System, Yu-Gi-Oh!, Pokémon, Warlords, Hecatomb, Anachronism, and various others. The Magic templates have grown to include nearly every variety printed by Wizards, as well as several custom templates as well. The program features a variety of features to improve the ease with which cards can be created, including text shortcuts for symbols not on keyboards, a random booster pack generator, a wide variety of statistical information, and an automatic keyword system up to date as of Conflux. There are also completed translations for Spanish, Italian, Japanese, German, French, Danish, Polish, and Chinese (both Traditional and Simplified). A full list of available templates can be found on the download page for MSE.
MSE vs. Adobe Photoshop
While MSE is good for creating decent renders quickly, the quality of what it produces doesn't match card renders created by Photoshop, mostly due to the quality of the images utilized in the templates. Originally, lower quality images were used to save on download size, and this has not been an easily reversed trend. It also does not have as sophisticated text-rendering technology. However, because it's designed for creating and documenting Magic sets, it is helpful for creating a database of created sets, and because there is a fair amount of effort involved in rendering cards in Photoshop, it is much more practical to use MSE for rendering an entire set.
Exporting to Other Programs
MSE Magic templates include the option to export to various digital tabletop programs, such as Apprentice, Magic Workstation, and LackeyCCG. MSE templates also exist to export Magic sets as HTML files, XML files, and plain text files.