Some time ago I downloaded a Lightroom plug-in by Jeffrey Friedl to integrate uploading photos to Flickr into the export menu. Note: the first hyperlink is to the plug-in, the second to his blog--a must for Japan photo lovers! You can also click here for the plug-in.
It took a lot of hassle to get it going--whether that be my incompetence or the complexity of the chain of software...
First, you must find out that you need Lightroom's "Plug-in Manager" (lower-left corner of the LR export menu screen, see the image right here) to install the thing.
Then, you have to find out that the plug-in does not automatically show in the export menu, but has a separate "header" (see the upper-right part of the picture).
Third hurdle: it takes some figuring out when exactly to log onto your Flickr account: before you start the export, in order to get the authentication process right.
It took me quite a number of tries, I admit, but when all is right, things go quite smoothly and it runs as smooth as a well-oiled bicycle. No more hurdles: the photos are online! It really is a shortcut now, from LR to my photo stream on Flickr in one go.
And at the same time my 6-week trial period is over... OK, I feel ready to register now (though that is not quite for free; the plug-in is "donation ware" or restricted to 10 photos at a time. Take your pick!).