There are a vast number of useful applications for business:

Microsoft Office 365 is the bare minimum to conduct everyday business with the included products of Excel ( spreadsheets and data analysis ), Word ( documents and publishing ), Outlook ( robust hosted email client ), OneDrive ( cloud storage - up to 1TB with an Office365 subscription ), Skype ( calling, chatting, and video ), Powerpoint ( presentations ), Access ( database and sql tool for non-programmers ). 

Then there is Freshbooks or Quickbooks for basic accounting. Expensify for expense and receipt management. 

Slack for team organization and communication and sharing. Asana is also great for team communication and project management.

Square allows everyone to accept credit cards with a simple rate plan. 

I hope that helps.