Uchiha's have a unique bloodline ability known as the "Sharingan". A Dojutsu [Eye technique] which changes the eye iris to a deep red color with little black markings on them. The maximum is 3 markings but depending on how skilled you are with the Sharingan, there may only be 2 or even 1 marking.
The Sharingan allows the user to see an object's next move. Allowing for the user to suddenly change their movement pattern to successfully dodge incoming attacks. The most interesting ability about the Sharingan is it's ability to copy any technique he/she sees, or has seen before. However, they cannot copy any techniques of Bloodline origin or summon creatures whom they haven't made an agreement with. Because of this Sharingan ability, a Uchiha member can have a vast amount of techniques backing them up in their arsenary.
Sharingan is believed to have evolved from the Hyuuga clan's "Byakugan", and like the Byakugan, can allow the user to easily see through illusions. Also like the Byakugan, the Sharingan has a weakness. It has rapid Chakra drainage, and it's best to use it sparingly. But unlike the Byakugan a Uchiha member is not given Sharingan at birth. It must be activated, which only happens in threatening danger, or some other kind of desperate need. However, once it's been activated it can be used whenever desired.
Uchiha's trademark techniques are in the Fire Element category, and is where their clan logo originates from. It symbolizes a fan wich feeds the fire. They say your not classed as a Uchiha until you have mastered one of these Fire Elemental techniques. Their are 3 main attacks, and probably many more variations, which have not yet been revealed. The first and most common one being the Katon Goukakyuu no Jutsu [Fire Element; Grand Fireball], where the user shoots a large fireball from his/her mouth. Thought of as a much to advanced technique for a Genin to ever learn, most Uchiha clan members learn this while still in the academy. More advanced versions of this are the Katon Housenka no Jutsu [Fire Element, Phoenix Fire], and the Katon Ryuuka no Jutsu [Fire Element; Dragon Fire Technique]. The Ryuuka no Jutsu is basically a much more powerful version of the same attack, and the Housenka no Jutsu is multiple fireballs shot out, often times with kunai knives inside.
Sharingan is the next step beyond Fire Elemental Techniques. But to go beyond that is a higher level of Sharingan, known as "Mangekyou Sharingan". Apart from looking a bit different, it is incredibly more powerful. For more information on the Advanced Bloodline abilities of the Sharingan,
Kekagenki
Translating in English to the Copy Wheel Eye This Bloodline Limit, allows it's users to copy and forever call upon just about any technique it is witness to. In addition to that it can see through nearly any kind of illusion, and hypnotize it's opponents.