GUI's compared

Does anyone know if there are any free GUIs other than Arena? I like Arena, but it has frequent errors on my computer for some reason. But I'm really not willing to pay for a proprietary one.

Tarrasch and Winboard are free.

Thanks, I'll check those out. They both sound useful (for different situations).

Not sure why my Arena is so buggy, though :(.

Anyone have comments on the Sigma 6.2 GUI?  It works well now with iMacs.  Has anyone compared it with Deep Shredder or Fritz?

Zarkon Fischer reports that the Shredder Classic 2 trial available in Chess.com Downloads can be reinstalled after the trial period is over.  It is a very good free GUI for playing against.