Starting is difficult. Here’s a list of business resources you may find helpful.
Invoicing: freshbooks, excel
Payment: Paypal, Square
Accounting: quickbooks, xero, inDinero
Payroll: paychex, adp, intuit, workday
Group collaboration: google docs
UX/design testing: usertesting
Web analytics: google analytics, crazy egg, kissmetrics
Mobile storage: box.net, dropbox
What else should I add to the list?