For one of our products (pmScrum) we've implemented recently the infrastructure and processes to offer and promote it via the SaaS model.
You can now try out the product via a demo site (click here to start) and we have a free subscription model available to evaluate our product more thoroughly.
Setting up the website was easy, but the whole logistics behind it required actually lots of work and quite some business process re-engineering. And the good thing is that this triggered a movement in our company to do full monty Agile (mainly Scrum and a bit of Kanban) ;-)
I'll be posting our experiences on becoming a real lean and agile organization here and on our pmScrum blog
So follow me or bookmark the site, if you're interested to know what we do.