Well now that we know that Rhys Ifans will in fact be the (or one of them) villain in the Spider-Man reboot, I figured i'd shed some insight on who he could play.
1. Carnage- Cletus Kasady
Carnage was the combination of a symbiote spawned from the original Venom symbiote and a crazed serial killer, and former cell mate of Eddie Brock. He thrived on murder and chaos and was many times stronger than Spider-Man.
2. Chameleon- Dmitri Smerdyakov
A Russian spy with a knack for disguises. He was the very first colorful supervillain Spidey has ever faced.
3. Electro- Maxwell Dillon
An emotionally stunted man with an inferiority complex, struck by lightning while working on power lines and discovers that he has a supernatural control over electricity.
4. Lizard- Dr. Curt Connors
When he lost his arm during a war, Connors felt like he lost a half of himself. Obsessed with regaining his lost limb, he creates a serum from reptilian DNA, in hopes of gaining reptile-like regeneration abilities. He regains his arm, but at a price: he becomes a humanoid lizard, with a savage personality.
5. Morbius- Michael Morbius
A Nobel Prize-winning biochemist, attempts to cure himself of a rare blood disease with an experimental treatment involving vampire bats and electroshock therapy. He instead becomes afflicted with a far worse condition that mimics the powers and bloodthirst of vampirism. Morbius now has to digest blood in order to survive and a strong aversion to light. He gains the ability to fly, as well as superhuman strength and healing abilities.
6. Mysterio- Quentin Beck
A disgraced stunt man and special effects artist dons an extravagant and theatrical costume as Mysterio and seeks to discredit and frame Spider-Man.
7. Scorpion- Mac Gargan
Private investigator paid by J.J. Jameson to undergo an experimental animal mutation therapy, imbuing him with super strength, speed, and endurance at the cost of his sanity. Donning a scorpion-based costume, he set out to defeat Spider-Man numerous times and take revenge on Jameson for taking away his humanity.
8. Swarm- Fritz Von Meye
A former Nazi scientist Fritz Von Meyer was a bee keeper in South America. When a colony of mutated bees devoured him, his consciousness was absorbed into them, becoming a living swarm.
9. Venom- Eddie Brock
When Spider-Man rid himself of the alien symbiote costume he acquired during the secret wars, it bonds with reporter Eddie Brock, who hates Spider-Man for causing him to lose his job and reputation. The symbiote, known as Venom gives Brock all of Spider-Man's powers, protection from his Spider-Sense, and the knowledge of Parker's secret identity.