BSG uses Tcl extensively in-house and on projects. At BSG they do something called hybrid-mail. This means they take documents (mostly soft copy) and deliver them multiple ways (e.g. high volume printing/inserting & postage mail, email, fax).
Their biggest Tcl use involved building the USPS mailing online system [L1 ]. There is over 125k lines of Tcl driving the system (web site, document manipulation, scheduling, distribution, high volume printer controlling, postage mgmt, address standardization, mail prep and envelope inserting).
And the USPS allows you to bypass their MOL (mailing-online) web-interface by using XML & their MML DTD directly. (need to dig up contact info to post here on the Wiki.) During a conference call with the USPS folks last week they asked "so what are you going to use to generate your XML, VisualBasic?" When we said "no, we use Tcl", they were suprised and said (paraphrasing), "Hey, that's cool! That's what we use!" -- Michael A. Cleverly
-- Todd Coram