<p>Yup, long title.  I've been programming in PHP for the last 6 years or so for work and personal projects, but I've got an idea for a desktop app (which incidentally, uses a web REST api).</p>

<p>I'm debating on how to approach this - I've got some experience in Java, C++, Perl and Python, but have never had the chance or opportunity to write and distribute an app to others of any significance.  </p>

<p>The app will need to communicate with a REST API (with OAuth), as well as access the file system, and possibly do some image manipulation (encoding/resizing, but this is a nice to have). I've been thinking something on .NET, but AIR is a possibility too (though I really dont want a huge runtime hanging around, this will be a system-tray type app).</p>

<p>I'm not looking for someone to write it, but I could use a nudge in the right direction. </p>

Being a Delphi programmer for years, you can do everything you want with it.
I'm starting to use C# at work. It's a great language too, but for a distributed application. the .NET framework still stops me from using it for my personnal apps.
In my point of view, Delphi is a good option. You can look at Lazarus/Free Pascal if you want a free IDE.
With this option, you build your EXE and that's it. Ship the EXE to the customer and it's working. No need for DLL/framework thing to have on the computer.
Of course, if you're using database stuff or third party DLL, you must ship the necessary stuff with it. But it's simplier than with VB with all the vbrunxx.dll, or with all .NET language.
It's my 2c... I think I'll be flamed for this! ;-)
HTH