http://www.tortoisecvs.org/ - integrates with Windows Explorer right-click menu, not as comprehensive as WinCVS but has everything most people need. Try this one first and only go to WinCVS if you need more.
http://winmerge.sourceforge.net/ - graphical tool for compareing and merging different files and directories (e.g. your deployed twiki server and your local twiki-cvs copy). If you haven't upgraded to v2.x yet, do so; The usability score went way up.