Simply write your code in an editor which supports copying code *with* formatting (e.g. as RTF), such as WordPad, Visual Studio, TextMate and Notepad++.
You can then copy the code directly into Powerpoint, preserving the formatting and syntax highlighting.

I prefer using TextMate on OSX. In TextMate, simply highlight a section of code, then click `Bundles > TextMate > Copy Selection as RTF` and paste this straight into Powerpoint. This will preserve the highlighting used by your TextMate theme, which you can change via `View > Theme > `

You can further mimic the font, which you can view in TextMate by `View > Font > `