Recomendation for a sticky-note software with a "connection" function?

Mac computers come with their own post-it-notes, called “Stickies.”

http://www.dummies.com/how-to/content/how-to-use-virtual-stickies-on-your-mac.html

I use them all the time.

I like using Springpad. For the PC, just Google it. For iPhone and iPad, you can find it in the AppStore. It’s free. It’s great for filing away, storing for future reference, writing down ideas and to-do lists, etc. What I like about it is that the saved info is in the “cloud” (i.e., Springpad’s servers), so (1) you don’t have to remember to back it up [unless you want to], (2) you can share and invite others to cooperate on your project, (3) your data is available everywhere you go, all you need is an internet connection. But, as far as I know, it does not have the type of “connection” feature you are looking for. However, it does have additional features, such as if you save the name of a book that you are thinking of reading, it will inform you as soon as the book is on sale somewhere.

Top Notes is another app similar to Springpad.

And there’s also Evernote, Box.com, Google Docs, and Dropbox. These are all cloud-based apps with robust collaboration features. You and your colleague can be working on the same document at the same time.

YOu are looking for mind mapping apps. I found one on the app store.
Here’s a search