I've installed cshell on Ubuntu 12.04, but there's no .cshrc file (either in ~ or /etc) - is it safe to create 1 to put a source to a script file, and if so, where's the best place to put it?
Yes, it is safe to simply create new .cshrc in your home directory. I would suggest using tcsh as better csh replacement - it is backwards compatible with csh and will use the same .cshrc file.
I personally have been using tcsh on FreeBSD for many years, and it was pretty good as interactive shell.
However, be warned that some people consider that using any shell from csh family is bad practice http://www.faqs.org/faqs/unix-faq/shell/csh-whynot