Zoho Invoice - 100% free online invoicing software for small businesses.
Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
FreshBooks - The ideal accounting software for small business owners.
Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.
Invoice Ninja - Invoice Ninja is a free, open-source solution for invoicing and billing customers.
Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.