When the player destroys the final component of the rogue VI (Virtual Intelligence) on Luna, there is a block of binary displayed as the last gasp of the dying VI. The binary displayed is 01001000 01000101 01001100 01010000 which when translated to ASCI reads "help".
When landing on Earth's moon one can find the wreckage of a probe called "CCCP Luna 23". The Luna 23 is a Russian probe that was sent to the moon in 1974 to bring rock samples back to Earth. It was damaged during it's landing and stranded on the surface.
If Urdnot Wrex is in Shepard's team and Shepard speaks to General Septimus in Chora's Den, Wrex makes the comment:"How did your kind ever defeat us?" to which Septimus replies "I may be drunk, Krogan, but you're ugly. And tomorrow I'll be sober." This is a reference to a phrase allegedly spoken by Sir Winston Churchill to Bessie Braddock when she accused him of being drunk.