The Most Notable Changes for 2011

Drag Reduction System (DRS). 
The adjustable rear wing would only be available under certain conditions; namely, drivers will only be able to use it when they are within one second of the car in front, but it would not be usable within the first two laps of a race except in the case of an early safety car. Furthermore, the drivers will only be able to use the adjustable wing on a designated area of the circuit, to be decided by race director Charlie Whiting. The system is expected to offer drivers an additional 15 km/h (9.3 mph) when passing, and will deactivate when the driver first touches the brakes after using the rear wing. Use of the system is prohibited in wet conditions. In order to illustrate the effects of the device, all circuits will have special track markings in a designated area of the circuit, the only place where the DRS can be used. Lapped drivers will be permitted to use the Drag Reduction System to un-lap themselves. 

Pirelli chosen as the tyre supplier for 2011 (see a photo of each of the new colors here)
The twelve teams moved to establish a close alliance with Pirelli to prevent any individual team gaining an unfair advantage, through the sharing of all tyre information. The Pirelli logo on each tyre will be colour-coded to identify each compound and tread pattern being used. Cars will have a mandatory weight distribution, reported to be a ratio of 46:54, to provide Pirelli with a technical specification, and preventing teams making changes to the internal configuration of their cars should they prove not to suit the cars. During the first test session of the season in Valencia, several drivers reported that they experienced much greater wear when using the Pirelli tyres, with Nico Rosberg and Lewis Hamilton suggesting that more than one tyre stop would be necessary in the races. At the final test in Barcelona, it was revealed that drivers would need to make three pit stops at most races. Teams will continue tyre development throughout the season, with the FIA approving additional sets of tyres to be used for development during Friday practice sessions. This will include the development of an experimental "fifth compound" known as the "extra hard" tyre to be used at certain circuits such as Istanbul where the demands on tyres are considerably greater than at other circuits. 

KERS units will be optional for all teams, after not being utilised in 2010 following a team agreement banning the devices. Although a proposal by Flybrid to provide mandatory units to the entire grid was not approved, to encourage all teams to run the system the minimum weight of the car will increase from 620 kilograms (1,367 lb) to 640 kilograms (1,411 lb), compensating for the extra weight required. 

107% rule in qualifying.
Under this arrangement, any driver who fails to set a time within 107% of the fastest lap in Q1 will not be permitted to take part in the race; for instance, if the fastest lap is 1 minute 40 seconds, a driver must set a time faster than 1 minute 47 seconds in order to make it to the grid.

Maximum allowable penalty 
Racing stewards can issue to teams from $100,000 to $250,000, after the 2010 German Grand Prix where Ferrari were fined one hundred thousand dollars for the use of team orders. Following the final race of the 2010 season, FIA President Jean Todt revealed his stance on the use of team orders, promising regulation of the practice rather than allowing them outright. Todt disclosed that while team orders would not be banned, any team using coded instructions would be prosecuted as such messages would be used to deceive spectators and would require teams and drivers to lie to stewards in order to substantiate the claims made in the message.

Other Technical Changes

1. Maximum height of the diffuser will be cut from 175 millimetres (6.9 in) to 125 millimetres (4.9 in) and the double diffuser designs, introduced in the 2009 season, will be excluded, in order to reduce aerodynamic downforce and turbulent air
2. Double exhaust-blown diffusers are banned.  They use exhaust gases re-routed over the diffuser to increase downforce , although single blown diffusers are still allowed. 
3. "F-duct" systems are banned, developed by McLaren and copied by other teams, as the system relying on drivers blocking a gap in the cockpit was judged unsafe. 
4. The number of wheel tethers doubled.  Load-bearing cables connecting the wheel hubs to the bodywork – will be doubled for 2011, in response to an increasing number of accidents where wheels have been torn free of their mountings, including the death of Henry Surtees in a Formula Two race at Brands Hatch in 2009. 
5. Aerodynamic wheel spokes are banned
6. Flexible front splitters designed to lower front ride height, and modifications to the monocoque that create a V-shaped channel running the length of the car's nose are banned. 
7. The maximum aspect ratio of the "bladed" rollbar structure – pioneered by Mercedes to decrease the obstruction of air to the rear wing – has also been reduced. The 2011 Lotus T128 and Force India VJM04 cars were both launched with a similar device, based on the same principle as the Mercedes device, but the Lotus and Force India variants are legal under the rules because the blade structure is thicker than the one developed by Mercedes. 
8. Gearboxes must now last for five races instead of four. Drivers will have one additional gearbox that may be changed without penalty for the purposes of completing an event.
9. The FIA has tightened its driving standards, moving to prevent overly-aggressive driving and driving beyond the boundaries of the circuit to gain an advantage by implementing stricter penalties for drivers observed to be doing so. 
10. A Pit curfew has been implemented, barring team personnel from accessing the circuit between the hours of midnight and six o'clock in the morning following concerns over mechanics spending all night performing repairs in the pit garage and the following day in the busy pit lane. In the event that this rule is broken, both cars for the offending team must start the race from pit lane. Teams have been given four "jokers" to use throughout the season, occasions when they are entitled to remain in pit lane overnight.
11. Team members deemed to be in key roles – i.e. team principal, sporting director, race engineers, team manager and technical director – will have to undergo accreditation for a "competitors' staff license" in order to maintain their positions within their teams. This is seen as a reaction to the actions of disgraced former Renault team principal Flavio Briatore at the controversial 2008 Singapore Grand Prix and applies to all key staff in all FIA-sanctioned World Championships, including the World Rally Championship, World Touring Car Championship and GT1 World Championship in addition to Formula One.
12. FOM has announced that all races will be broadcast in native high definition format from 2011, having previously experimented with it at the 2009 Abu Dhabi Grand Prix. Several broadcasters have confirmed plans to broadcast races in the new format.