GH - Just found this: Stickies by Zhorn Software - http://www.zhornsoftware.co.uk/stickies/

Seems to have a lot of good options... alarms and hiding as you requested. While it doesn't have an explicit syncing ability, according to the description: Stickies stores information in a single text-based ini file. Sounds portable, too. Does not write to registry or do anything with system files.

So, if you use something like Dropbox, you could keep the program (or perhaps just the .ini file) in a Dropbox folder that syncs to all your other PCs.

Works on XP through 10, is freeware, and I believe there's a Unix version. There's also a few really good tools that add more options & functionality such as tags and filtering notes so that only those with "X" tag show up and others are hidden. And even a Windows 7 import tool to import all your Microsoft Sticky Notes into this app.

Also, look at the Skins section for more customization. The developer seems to have really put in some TLC in this one.

Let me know what you think.

EDIT:

Ok, looks like it may be more involved than what I suggested with Dropbox. Read this article: http://www.zhornsoftware.co.uk/support/kb.pl?q=00002 on portability. Also, there's a "PortableApps.com" version. The link is at the bottom of Zhorn's support article. I would try downloading portable app and placing it directly into the Dropbox folder on your desktop.

Worst case scenario, you could just keep this on a stick drive.

Lastly, I forgot to mention there's a ton of language packs available for this as well.

Thanks! This is exactly what I was looking for.

Google Keep is in second place, so thanks everyone for recommending that one as well, but 7 Sticky looks really nice.