Hi,
I left Poly and joined the Civil Service as a programmer many moons ago. Here are some things I found over the years....
UNIX Shell programming is useful and having a scripting language like Perl to back it up makes for a very good combination (which is what I use for backend work). Perl has advantages over C, mainly I found it easier to write and understand. Also has disadvantages in that it's not as quick or low level. Other scripting languages worth considering might be Python and Ruby though I know little of these.
Relational databases are used in most places so a knowledge of SQL is also good to have. Probably ANSI SQL rather than a specific variety such as Oracle.
Some knowledge of Java is useful these days as this can be applied in many places, both on the front and backends of applications e.g apps, web-pages, J2EE etc. Also kind of forces you into good programming practices too using OO concepts etc.
A background knowledge of different application architectures such as 2-tier, n-tier using middleware, and J2EE would be useful as lots of organisations use a combination of these depending on what each application does, it's workload etc.
Finally, you might want to consider looking at a 4GL language, an example being PowerBuilder which from a brief look I thought seemed pretty good. I develop in a 4GL called OpenROAD (used with an Ingres database), which whilst it isn't widely used, is used by very large employers e.g government etc. Quick to develop in, has an OO basis and, whilst undoubtably old fashioned, gets the job done. If you're interested it's got a bit on Wikipedia or I can give you more info.
I find that it's not so much learning all the syntax of languages that's important. It's more knowing what the language can do and where to find out in detail when you want to do it that's important.
Hope that helps a bit.
Jim