Now there's nothing that should stop you from Ajaxifying your web applications. As indicated by my previous post, I'm an absolute beginner at building mash-ups. If you are as well and want to get started, here's what I suggest:
What do you want to create a mash-up on? Look around, there probably are a few ideas out there that will inspire you. The programmable web is a great resource. http://www.programmableweb.com/
I'm sure you can create something new. You very likely have a unique value proposition to make. Things unique about you could be:
Just one source! http://dev.live.com ENJOY.