Do you mean granite blocks from the likes of Audio Serenity (or the more cost effective Tesco chopping blocks) ?
Or a more high-end solution in the form of proper stands e.g. The Audioworks in Cheadle do some special stands for floorstanders : "MusicWorks ReSponse floorstanding speaker stand. Priced from £200 / pair depending on configuration, these stands can transform the performance of even some of the best floorstanding loudspeakers"