Delivering constant value for your customers. Especially since they pay you every month again and again. This means you have to ship. Again and again.
Year - Ship a major version of your product. A real new capability, something worth "launching" and talk about with analysts.
Quarter - Launch a minor release that answers your customer needs and questions, and that fixes product issues or bugs
Month - Release small new improvements that may not count as a release, but are meaningful enough to mention in your customer newsletter
Week - Ship things that are meaningful for your team. A new ability to do marketing or a new improvement to your churn reduction approach. This could be the launch of an online chat on your homepage or a new campaign.
Day - Ship a blog every day, or a new idea that you execute on.
Shipping is very satisfying and great for team morale as well. In the traditional software business, we used to make trophies to celebrate shipping. SaaS does not really warrant this anymore since we are now constantly shipping. It is kind of cool to do an award for your team once in a while. Some nostalgia in the picture below, from creating an ISO Standard, shipping major releases of Microsoft Office to creating a new Cloud SaaS ERP product.
If you need some tools to ship, I recommend Seth Godin's article and the ship-it journal that you can download here.