What are some useful SaaS tools for small businesses?

If you are just getting started, you will need some basics like accounting, banking, email, document management and possible CRM. You can get all of these services as SAAS. For example, we use Office 365 for email and document management.

You can avoid significant up-front capital expenses by starting with SAAS for your core services - typically pay by the user or a flat monthly fee - a lot less expensive that implementing these services on premise.

We try to implement as many of our services as SAAS as possible because it means we don't need to manage the systems and software for these services. It's been working for us.

if staff availability is critical, i would recommend WhosOff as a vacation request, approval and tracking tool.

have been using it for more than 2 years. very happy so far.

Expensify is a good one. Very cheap, only pay when you use it, and pay on a per person basis, not for the entire company. Nice phone app, too. Very handy if you have any measure of T&E. And not to be understated, it's so cheap and easy, even if you use Excel you will want to at least check it out. https://www.proformative.com/products/expensify-expense-reporting-reviews.