1) Zim, alternate to MS OneNote in Windows
Download Zim, available in Ubuntu Software Center
You can take your notes, create pages, add attachments, images and provides additional functionality like task list manager. I store and access my Zim note from dropbox, so you can access it from anywhere as long as you have Zim installed in that computer. Good news is Windows version of Zim is available.
2) Parcellite, Clipboard Manager
Download Parcellite, available in Ubuntu Software Center
A tool to preserve your history, by default 20 copied items are preserved in history. You can increase it to maximum with preferences option.
3) BleachBit, alternate to CCleaner
Download BleachBit, available in Ubuntu Software Center
No much explanation is needed, we all love CCleaner and will miss it in Ubuntu. BleachBit provides similar solution in Ubuntu but not all features of CCleaner. Remember that your history items in Parcellite are still preserved and not deleted while cleaning with BleachBit.