Here's a free online service which will make you think one of 2 different things. Either you'll reckon it's a hideous invasion of privacy, or you'll think it's the biggest improvement to your online presence in years. Or possibly both.
The service in question is called If This Then That, or IFTTT for short (it's pronounced like Gift without the G). You can find it at www.ifttt.com and it works with just about all major browsers.
IFTTT allows you to construct rules, or recipes as the site calls them. A rule lets you specify that if a certain thing happens on one site, then automatically do something else on another site. As to what happens, and what you can do in response, it's all tightly controlled and easy to manage by simply selecting from lists.
The service supports dozens of third-party sites such as Facebook, Twitter, Gmail, Pinterest, Tumblr, Dropbox, and many more. A typical recipe might say "If someone tags me in a photo on Facebook, send me a message about it on Gmail". Or "If someone mentions me on Twitter, send them the contents of a file from my Dropbox".
Needless to say, the system needs you to grant it access to your accounts on any services which are the subject of a rule.
As I said, invasion of privacy or the best thing since sliced bread. Whatever the answer, you have to admit that it's extremely clever and definitely worth a look.