This isn't really Tiddlywiki per se but it is kind of related. I use a TW to curate links to things. Plus I'm often sharing via Twitter etc. so I built this little bookmarklet that lets me easily grab the title and URL of a web page.
More details and the bookmarklet can be found here:
There used to be ways to do similar and put the info directly in your computer's clipboard but browsers got more security conscious about such things so there is an intermediary dialog box that you have to copy out of. Still, saves a bunch of time retyping things.