I bet DB2/UDB is still around and kicking, if nothing more for legacy support. Theres also Sybase, but they've fairly much stagnated and jacked up their pricing, so the companies I've worked with that used Sybase either have or are working to migrate to MS SQL.

There are other esoteric DBMS's, such as IMS which is still supported by IBM to the best of my knowledge (because that 40 year COBOL app still has to run).