Linux Unix basic command recommendations

I just received a beautiful brand new machine with Linux Red Hat 5. (Red Hat 6 does not support certain proprietary software). It is a fast machine with lost of speed, storage, and a high end video card. I will be using the machine to run graphics intensive software. I will also be using the machine to modify this software. In addition to software modification, I will be developing algorithms that use multiple languages including Fortran, C, Perl, & Python in addition to basic shell scripts. I do not need to know these languages in depth, but what I really need is a  basic foundational understanding of a little of the network of my system and linux/commands commands. I have root access. Is there a suggested list of basic unix/linux commands that would be appropriate? My knowledge is somewhat limited in the area but I have worked with unix/linux on a limited scale.