Current version is 3.5.1
This is reflected in the following files (sigh)

README
        For informational purposes
configure.in
        The patchlevel is either "" or ".1" etc.
        *re-run* autoconf to update configure
bin/httpd.tcl
        set v 3.5.1
        So it can look for the right tclhttpd library
lib/version.tcl
        To set the right version string.  This does
        package provide major.minor only, but the string
        has the date and patchlevel.  The actual value
        of the httpd::version package number isn't used.
lib/pkgIndex.tcl
        This needs to be regenerated when any package in lib
        changes its version number
DIST_build/DIST
        To choose the CVS tag for the release, which typically
        reflects the version number (e.g., tclhttpd-3-3-1 or
        tclhttpd-3-4-rel-2)
DIST_build/DIST.exp
        To remove the scratch directories used to create the distribution
DIST_build/Makefile.boot
        To fix the version number