Sybtcl allows you to write embedded SQL applications using Tcl instead of C (or COBOL, ack!). Since Tcl is such a quick and easy language to develop in and Tk gives you the ability to write X11 windowing applications with that same ease and speed, this means that you can whack together GUI database applications very fast. The code is readable and easily modified, and the speed is quite acceptable for most normal database apps.
Tom wrote an X11 interface for Sybase TSQL called wisql (Windowing ISQL) which I have remodelled extensively over the last year. My version is known as uco-wisql, and his is now known as "wisql-lite". uco-wisql is included in the sybtcl release, and you can get the latest version from my site: ftp.ucolick.org. (ftp.ucolick.org, in pub/UCOSYB)
Locally our OLTP sybase system uses a forms interface for data entry and browsing which was entirely written in Tcl/Tk and embedded SQL. It's quite robust, easy to modify, free, and less than 10K lines of code. Currently it offers about 75 different forms to users through a menu interface. See the fosql writeup for more details. We also have a sybase perfmeter which monitors server activity, written in Tcl/Tk. It's packaged with wisql.
If you combine sybtcl with tcl-dp (or the TclX interprocess extensions) you can write, for example, a SQL serving daemon which permits machines without DBlib support to submit SQL queries and have them resolved through your sybase server. I use it with tclXess to give users the ability to import data directly from Sybase into their spreadsheet. The sky's the limit.
For a long list of other cool Tcl/Tk extensions besides sybtcl, click here. Tom has written an oratcl extension, for those who have to deal with Oracle.