Coccinella is a free and open-source cross-platform communication tool with a built-in whiteboard for improved collaboration with other people.
Sticky notes/post-it application for linux
MyNotes is a sticky notes/post-it application. Notes are created using the system tray icon. They can be organized in categories and each category has a color. Images, checkboxes and a few predefined symbols can be inserted in the notes. The style of the text can be changed (alignment, style, color).