Professional experimental physicist here.
There are two main types of software physicists have to deal with: hardware interface, and data analysis.
Hardware interface is often the the tougher one: slow controls, data aquistion, environmental monitoring - these all need to interface to hardware through various drivers. LabView is an obvious candidate for table-top experiments, since it is possible to set up working control and readout systems more or less out of the box. There is really no good open-source solution for this for the same reason that open-source drivers took a long time coming to Linux: the user base is just too small to write the code.
My own experience is that it's far better to write your own code, using whatever drivers you can scrounge - it's far more efficient at getting what YOU want done as quickly as possible once it's running. However, the time to write and debug this code is extensive. It's particularly bad since often students will write this code and then disappear, leaving you with badly-documented half-working code.
However, this is basically true of many LabView installations as well.
On the data analysis side, there are many good packages that serve as starting points. ROOT (http://root.cern.ch) is an excellent package for doing event-based data analysis in nuclear and high-energy physics, including efficient ntuple storage and histogramming. It's really a toolkit, not a program, so it allows you to do your own analysis by writing your own code.
I'm not familiar with other big packages, but I know that I frequently use raw C, C++, gnuplot, perl, and python to do little jobs.
There are other tasks as well. Blogging software can be good for logbooks. Wikis are good for in-house documentation.
It really depends on specifics. But basically it depends on where your project falls on the quick-and-dirty vs long-life vs high-performance judgements.
