If you use Flickr a lot to store your photos online, you might find the free app Flickr Streamr useful.
Flickr Streamr is designed to make transferring photos from your device to your hard drive and onto Flickr simple, and without uploading duplicates. It also has a system to automatically rename photos according to the time and date they were taken, making it easy for you to locate pictures.
The application is organised in three panes: one for your camera, one for your hard drive, and the last for Flickr. You can compare flies between the first two, and make sure you only transfer files you need. From there, you can drag and drop files into the Flickr window to upload any you want. This requires authorizing Flickr Streamr with access to your Flickr account, which is pretty simple.
While the application works well in that direction, there is a download from Flickr button, but it doesn't seem to work. The Interface in general is functional, but not very attractive. While Flickr Streamr functions well as a Flickr uploading tool, it's hard to see why you'd choose it over major image managers.
If you're looking for a quick and easy way to make multiple uploads to to Flickr, Flickr Streamr is a simple and lightweight option.