There are different views for different sects and madhabs.
Do not rest your arm as it makes you equivalent to a dog
Rest your arm on the ground
Also the following is stated on this website (Thanks to Gulshan)
The Hanafi Madh-hab
Allaamah Muhammad Amin Ibn Abidin as-Shami rahimahullah:
"A woman should not raise her hands till her shoulders. She should not take her hands out of her sleeves. She should place one palm over the other on her breast . She should bend only slightly in ruku'. She will not spread her fingers out in ruku' but rather keep them close together and place her palms on her knees without clasping them. She should bend her knees slightly. She should contract herself in ruku' and sajdah. She should place her arms flat on the ground. She should sit with her legs out and resting on her posterior in tashahhud. In tashahud she should keep her fingers close together. If any mistake occurs in salah, she should clap her hands without uttering anything. She cannot make imamah of a male. It is makruh to have a female only congregation. The female imam will stand in their midst. It is makruh for her to attend the congregation. In a mixed congregation the females will stand at the rear. Jumu'ah is not obligatory for her, but if she attends it, she will be absolved of responsibility. Neither is Eid compulsory on her nor the takbir of tashriq. It is not mustahab for her to perform Fajr when it brightens up. In the loud salahs she will not raise her voice. "
Most of the shias rest their hand on the ground, some don't.
Just a muslim
Bukhari :: Book 1 :: Volume 11 :: Hadith 604
Bukhari :: Book 9 :: Volume 91 :: Hadith 352
... He also mentioned some other things which I have (remembered or) forgotten. The Prophet then added, "Pray as you have seen me praying and when it is the time for the prayer one of you should pronounce the Adhan and the oldest of you should lead the prayer.
As you see in this women should pray as men as nothing special is specified for women. Thus raise your arm from the ground.
[Proof for hanafee] This & this
Rest are from observation