Rachel Whiteread created one of the earlier 4th Plinth commissions. Currently there is a major retrospective of her work at Tate Britain. If you are interested in her work generally it is an excellent exhibition - in a fully opened out gallery space which seems to really suit her work.
The main exhibition is ticketed, but the model for the Fourth Plinth piece is in the public shop area outside the main exhibition - and so can be viewed for free. Alongside some drawings and information about the work.
The effect of the resin material can really only be appreciated in the flesh and does not represent well in photographs. I would like to have seen the full scale piece in situ, but sadly I didn't.
News and progress from the group