LR/Mogrify is very nice, as is the SmugMug or flickr plug-in's from Jeffrey Friedl. They are not truly free as they once were...the developer(s) has had to move to a donationware model due to increased demands to keep the plug-in's current. So, for Jeffrey's plug-in's one can donate via PayPal ANY amount, even a penny, then get a serial number to register the plugin before the 45-day(?) grace period.
There are a bunch more I have on my list to look at but those three I use a lot.
Here is the link to Jeffrey Friedl's Blog and the SmugMug/Zenfolio/Flickr/Picasa/Facebook (and other) plugin's for LR:
http://regex.info/blog/lightroom-goodies
Here are a several nice plug-in's from LR/Mogrify:
Photographer's toolbox