On my Samsung Captivate (AT&T) they have (for no reason that I can fathom) split the voice command key out of the Swype keyboard. So, I seem to have to make a choice, do I want to use swype or have easy access to my voice command mic.
I was hoping there's some way to add a custom keyboard where either I designate the keys when I set it up, or (more ideally) they are already set up in the obvious way, but with both the voice entry available on the Swype keyboard.
There is a nice (free) alternative keyboard on the Android Market - that is somewhere between Swype and the built in keyboard - called TouchPal. It allows for three different layouts (16 key, 20 key and QWERTY) and you can set a default for different orientations - i.e. 20 key for portrait, QWERTY for landscape. And there's a bunch of other things it does that make it nice and easy to use.
One thing to note is that it's made for Chinese and English input but there are options to turn off the Chinese input. Also, some version of Android have a bug that sometimes prevents a newly added input method editor (IME) from showing up properly. You may need to restart the handset after installing.
All that aside, I use it every day on my HTC Desire as a replacement for the stock keyboard and I couldn't do without it. Have a look at CooTek's Site or search Market for CooTek or TouchPal.
It is possible to develop your own keyboard input method. However, this isn't a trivial thing to do. You can either code it yourself or wait for someone else to do it. Sorry :-(