Tools for diagramming and sketching on Windows

Windows is a broken and barren desert of malware and spyware, but I still need to work in it. Alas, I can't switch at work (yet).

So, when I'm looking for better ways to diagram and sketch, I can't choose from the rich world of Mac alternatives, much less from iOS tools. I need something that will work on Windows -- or on a web platform our corporate software doesn't block (alas, Evernote).

I'm working on my options, but fwiw here's a list I'm assembling. I'll update it with whatever I like, while striking out those I've considered and eliminated.

Windows 

• OneNote 2010: popular, but tied to Office
• SnagIt Editor
• PowerPoint: Too awkward to just use for diagrams.
• Visio: Expensive, clumsy, overpowered, relearning curve with infrequent use.

Web

• Google Drawings: Current favorite
• Lucidchart (Google Drive/Apps): $$
• Gliffy Online
• Balsamiq Mockups (wireframe)
• Creately

Mac/Win

• Pencil Project - GPL, no documentation, no help file. Couldn't figure out rounded corner.
• Dia - GNOME Live! - Visio like
• yEd - Graph Editor
• ConceptDraw Pro $200