Kapsules is a Windows widget engine. It might even be called the next of kin of Mac OS konfabulator. So, let's take a closer look.
Kapsules is a free software with all related advantages and disadgantages. Released by Carbon 6 it has all the defects of software, released by it. One of them is a feeling of an unfinished product. But, referring to the program's status (freeware) and age (less, than a year) this disadvantage is easy to forgive. The more, Kapsules is a really nice software.
In order to build applications (widgets) Kapsules uses Windows Scripting Host, so developers can use one of available languages (like VBS or JAVA Scipt) to build their applications. In order to create an application you'll need a special Wizard app (can be downloaded from the site), which slightly simplifies programming and get a version of tutorial. Sadly tutorial is only available online, so people with a limited internet access (like me) may be forced to download it manually.
Typical widget consists of at least two files: appname.kap and appname.config. The first one contains the code while .config is used to store widget's settings. As all the settings are stored in XML format, configuration files are not too hard to edit manually. The can also be some additional graphics (PNG files), stored in "resources" folder.
Even using a Wizard to build up your first widget you'll have to write all the actual code manually, so without a basic programming knowledge you won't be able to do a thing.
Surely, you can simply use widgets without making your own. At present time the number of widgets available is not too large: there are a couple of weather forecast displays, few meters and so on. Still not bad for an application, which release version is still 0.7 
Widgets are not static: you can configure them bu Shift+Right-clicking. Configuration often implies font settings, output info formatting, transparency, position and so on. Widget settings window itself is quite ugly , but I hope this improves in next versions.
Incomplete, slightly buggy (will it ever remove trash from the "about" window?) even today Kapsules seem to be a very interesting instrument. With more widget developers it might become even more popular. And even now it's a good instrument for developers, willing to create simple GUI applications without a need to learn GDI+ programming.
P.S.: before downloading Kapsules note, that in order to run it requires Microsoft .NET Framework, so you might need to download another 20 Mb. MS was always famous for "optimizing" its programs and libraries