Creating Flowchart diagrams in Visio is a bit tricky, and time consuming since its a full-fledge software which gives you somewhat unlimited controls towards your projects. Ascii Flow, is a free online tool which helps you out if you’re not getting along with Visio. This simple tool is easy to use and is completely text based; which makes it functionality less complicated. Internal tools available are select tool, click and drag tool, arrow, line, text an eraser tool. Rows and columns can be added to acquire more space and undo /redo shortcuts work like a charm on this web based app. Work can be exported as simple text or html.
It might not be the most recommended app if you are looking towards design and more collaboration with images but definately a great tool which can be used when unable to work with images and Visio.