Just some suggestions, you should also include all their competitors
kernel hacking: VMWare, Citrix and other virtualization providers. Maybe Google and Intel (think hyper-optimization companies and brand new hardware that needs drivers)
Databases: Oracle, MongoDB, etc
Networking: Cisco, Juniper, possibly finance & wall street companies
Distributed systems: Oak Ridge National Labs, research/academia, biotech
You should really talk to someone from a particular company you're interested in to find out their requirements. LinkedIn and your alumni network help with this.
General stuff would be good grades, evidence of leadership/positions of responsibility/working in teams, projects (academic is fine). Work experience in programming would be a good thing to have. If you have a masters they'll expect deeper tech skills--preferably in their specific vertical. You probably need to know at least 1 scripting language and 1 programming language, in this case probably C/C++, but they may accept other languages like Java.