First of all there's a SNOBOL4 Yahoo group where active discussions on SNOBOL4 and related languages take place. Also code samples and links are available from this group.
As mentioned in the previous post, one of the main resource sites is http://www.snobol4.org/ by Phil Budne.
A commercial implementation of a SNOBOL4 compiler called SPITBOL is available from http://www.snobol4.com/ .
I also learn about a SNOBOL4 IDE called TkS*LIDE. This IDE is written in TCL/Tk and it worked out of the box, in my Ubuntu machine. Here's a screenshot:
The Wikipedia SNOBOL entry is also good resource.
