"The Observer" can be seen at back when Mark Young exits from the elevator at the beginning.
From a street sign, one can see that Massive Dynamic is located on Bell Plaza, obviously named for William Bell - the founder of Massive Dynamic.
Olivia looks at an airplane ticket during her investigation. The carrier is 'Oceanic Air', the same air carrier in creator J.J. Abrams' show, Lost (2004).
The glyphs in this episode spell "Voice".
The FBI helicopter seen at about 38 minutes is a Eurocopter (Airbus) AS355 TwinStar. These are not seen too often. This Is a twin turbine engine version of the AS350 AStar, which is seen quite often in various movie and TV productions.