BLT is the best choice I know. It works, but the style is a little bit outdated. And i suppose it's out of maintenance? Since the lastest 2.4z was release in 2002.
Plotchart is another great chart library which is part of tklib and already builin in tcl 8.5. I tried some examples shipped with tklib, but it looks like it can only show static charts.
Is there any alternative library available?