Sketchfab have introduced an online modelling app, check it out here: https://labs.sketchfab.com/sculptfab/
It didn't work in IE9 but did in Firefox, though it kept asking for plugins it couldn't find. I haven't used it much but it works a bit like Sculptris, where you manipulate a mesh by pulling/pinching etc. It loads and saves obj files, here is Julius mek:
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The picture below shows a starting sphere which I have tugged around into another form
So far I have only really managed to mangle models. If you try it out let us know how it goes.