If you have an older Symbian or Windows Mobile device, it probably either came with support for Flash Lite 1, or no Flash support at all, whereas the newer devices are starting to be available with support for Flash Lite 2 content, which will allow developers to make use of more advanced programming features, not the least of which are functions. I suspect that this is going to motivate a lot more cross-platform application development for mobile devices, especially in the hobby and open source world where code signing costs and fragmented SDKs are a pretty significant barrier to entry.
Thankfully, last December Adobe released free end-user Flash Lite 2.1 installers for both Symbian series 60 and Windows Mobile platforms. So if you don't have the most recent hardware, you can perform a quick upgrade and extend the usable life of your device. For thos of you who are interested in developing Flash apps for devices, Adobe's dev center also has some decent starter howtos on the subject.
I'd love to get your opinions on mobile development. So if you have any thoughts on the subject or know of any good open source tools, guides or resources, please share them in the comments!