I recently discovered the excellent web based diagramming tool named Gliffy. You can think of it as a web based version of Microsoft Visio at a high level. In addition to network diagrams you can create flowcharts, org charts, sitemaps, user interface diagrams, etc. The import/export functionality works well and even supports importing Visio VDX files (not VSD though). Gliffy offers smooth integration with Google Drive.
A free account offers you the ability to test drive the capabilities of their platform with a few limitations including:
- Total diagrams are limited to 5
- Storage is limited to 2 MB
- Inability to create private diagrams (everything you create is viewable by anyone)
I encourage you to take their tool for a test drive at http://www.gliffy.com/