So far the list of rumours - unsubstantiated as far as I can make out - circling wildly on Twitter includes:
Tanks on the streets
Arabic speakers with Anti Riot police - possibly hezbollah (update: The LA times asserted as fact, then rewrote it seems)
Various Oppostion members "arrested"
Iran's electoral commission had declared the election void (it was a dissident sub set of staff)
The Army announcing it will be "neutral" (unsurprising - they are meant to be on side of "the people")
"Massive use of teargas"
Protestors captured weapons from a military base
"Staggering" numbers of injured flooding into hospitals
That the "real" voting figures are emerging giving Mousavi some 19m votes
Rafsanjani and Qom Masters "are going after Khamenei"
Protestors shot in the streets
Injured protestors turned away from hospitals
students killed and buried without families being notified
Ballot boxes were taken away and burned
(If you have others - or have proof of any of the above let me know)
There are and will be more
Some may be true. Some may be confusion. Many are planted in the hope of inciting more protests and support.... The trick is to tell which is which. I wouldn't trust any such reports without hard evidence.