While setting up the Bascom IDE for the Elektor Arduino bootcamp I also had to install the Arduino IDE.
The IDE can be downloaded from the official Arduino web page:
I first tried the recommended version 1.0.5.
However, while starting the IDE I noticed that there was a nasty issue with the COM port scanning algorithm: the whole UI froze for quite a long time whenever the ports were scanned (seems to be a windows specific issue, linux version should work ok). Luckily there was also a newer version (although tagged as beta) where this issue was fixed. So eventually I downloaded the version 1.5.6-r2.