This semester, I'm teaching a junior-level lab section. Consequently, there certain things I assume students have learned at this point, and know were covered in their freshman level courses. I don't know if it's an issue of retention, or that they never really learned it the first time around, but there are certain basics of report writing that they've just missed.
There's some of the higher-level style issues, like use of 3rd-person passive voice instead of first person active voice. But for some students, they may be unaware of even more basic issues. For example, recently, I encountered a student who didn't know about Microsoft Equation Editor or the symbol menu, and has been using wikipedia and copy-paste to put equations into lab reports. Multiple students had to ask how to take a text file of comma separated values and open them in Excel or another graphing program.
While I was initially rather stunned, thinking about it, we never actually teach students how to use much of the software we expect them to use regularly, like Microsoft Office. Even if they had been taught at some point, the GUI has changed so drastically over the last few releases that they may no longer be able to find the tools. Even though these students are "digital natives", not everyone can learn software by poking around until it does what they want.
What other skills do you assume students should have by college?