My favorite is AT Notes – a freeware. I'm using it since Windows XP and it still works consistently in Windows 8. It shows its presence via tray icon.
It is discontinued for years already, and the site is kept published against the will of ATNotes author. But the application itself is greatly useful, so until it works well, I recommend it.
- every note can have unique font, color, transparency and optional 2-color gradient
- selected notes can be always on top
- every note can be minimized (it expands to full size on mouse over the note)
- deleted notes go to recycle bin so accidentally deleted content can be recovered
- notes can be put into folders so you can sort them into groups
- there is a search available across all notes
- there is a global list of all notes available
- notes can be hidden, such notes are visible only in global list (for example reference cards you do not need all the time). It is possible that you find yourself with 200 notes, having 5 most important notes on desktop, all others hidden. This way you will soon redefine ATNotes as a handy database, not only desktop notes app.
- alarm can be set to pop-up individual note at given time (including playing custom sound or running desired application)
- if needed, alarms can be repeated daily or weekly
- nearest alarm is shown when hovering mouse over taskbar tray icon
- file paths in note text can be recognized and offered to open when a note is right-clicked
- besides the notes, there is also available a month calendar (it shows up to 12 months if its window is stretched)
- selected notes can be sent to peers through the network
- most of actions can be controlled by keyboard
- you can define global shortcut keys
- bring all notes on top, then put them back to desktop again
- show/hide all notes completely
- open search dialog to search through all notes
- you can assign global shortcuts like Ctrl+Windows+Letter so they won't collide with shortcuts in existing apps. Just make sure you are not overlaying existing Windows shortcuts.
- there are also fixed command keys available when a note has focus (e.g. E for edit, A for setting alarm, O for toggling Always on top, H for hide, P for print – see help for complete list)
Recommendation: as soon as you start using the app, copy ATNotes data files to your Documents folder and then in Settings, change the paths to point to these new files. This way you will have your data files always backed up when you back up your documents. Having data files in your closely watched folder is much better than to have these data files somewhere in Local Settings folder. This way you will never forget to migrate them to new PC.
If ATNotes is started before Windows allows applications to register their tray icon, it will display message Cannot register tray icon. Press Retry or Ignore button.