NumSum is a new community for creating online spreadsheets, tagging and sharing them.
I created a test spreadsheet you can view here.
It was rather simple to add a link, some calculating cells, and an image.
The interface mimics Excel pretty well. I did get a “There was a global error processing your request.” error every time I saved a spreadsheet, however the spreadsheet was saved anyway (no problem, just a quick scare 
NumSum was created by Metaha, who has a blog I just added to my feedreader, they discuss NumSum in this post.
Via LifeHacker. Here’s a screen grab:
