If your Mac is on 10.8 Mountain Lion, you can share just about anything via services like iMessage, Twitter, Flickr, Apple’s AirDrop, and Facebook straight from the Finder, no extra apps or browsers required.
As long as you add your service credentials to the Mail, Contacts, & Calendars pane, found under Apple menu > System Preferences, you can right click just about any file in the Finder and use the Share menu. Instead of opening a browser tap or separate app, a small sharing sheet will appear in front of your other apps. Some services will have customizable info—you can pick a Flickr set and privacy, add location to Twitter, pick an album, friends list, and location for Facebook—and you can share your file right from there.