I have made this simple preset for exporting files from Lightroom at a set width of 640 px, It creates a set width for either landscape or portrait. So landscape files that are created are 640 x 425 pixels and portrait files creates are 640 x 964. This creates a continuity of width on your blog if you have lots of photographs.
I’m still playing with this size as although I like the set width I think that the portrait files are quite large on-screen.
Click here for preset, to install it. go into the export dialogue box in Lightroom and under user presets right-click and hit import, then locate the file and add it.
I have a couple done for iPad size, I will upload them at some point.