Press ~ and type "map [level code]" too get to the corresponding level:
Single player mode:
Lower Mines: RMINE1
Mine Engineering: RMINE2
Thaelite Mines: RLAVA1
Tectonic Stabilizer: RLAVA2
Eastern Warehouse: RWARE1
Waterfront Storage: RWARE2
Logistics Complex: RBASE1
Tactical Command: RBASE2
Research Hangar: RHANGAR1
Maintenance Hangars: RHANGAR2
Waste Processing: RSEWER1
Waste Disposal: RSEWER2
Munitions Plant: RAMMO1
Ammo Depot: RAMMO2
Widow's Lair: RBOSS
Multi-player mode:
The Low Road: RDM1
The High Road: RDM2
Boxed In: RDM3
Razor Close: RDM4
Stone Hinge: RDM5
Nexus: RDM6
Sewer Citadel: RDM7
Styx and Stones: RDM8
Scenic Overlook: RDM9
Great Divide: RDM10
Dish It Out: RDM11
Fall From Grace: RDM12
Roads To Nowhere: RDM13
Rogue's Edge: RDM14