Since our iControl interface is a set of standard SOAP interfaces, pretty much any language you choose to write your application in will work. We have samples for perl, java(Apache Axis), C, and VB in the SDK to get you started.
The first step will be choosing a language you are comfortable in and have the development tools for. I can't really answer that question for you.
Next step is to get all the prerequisites for your given toolkit to support SOAP and SSL. For Perl, you'll need SOAP::Lite and Crypt::SSLeay. For Java, you'll need Apache Axis and the Java JSSE libraries, for .Net everything is included in the installation of Visual Studio.
We've got a few quickstarts available along with some video tutorials on the iControl tutorial page
http://devcentral.f5.com/Default.aspx?tabid=83
Click here
If you've chosen Java or .Net, then we have some helper libraries that make development very easy. Take a look at the iControl Assembly Labs project
http://devcentral.f5.com/Default.aspx?tabid=68
Click here
Documentation for the APIs as well as sample code are available online in the iControl Wiki
http://devcentral.f5.com/Wiki/default.aspx/iControl/HomePage.html
Click here
And you might want to download the latest SDK for more samples as well as a portable documentation set.
Hopefully this is enough to get you going.
Good luck, and let us know if any questions come up.
-Joe