Speedlight is the brand name used by Nikon Corporation for their photographic flash units, used since the company's introduction of strobe flashes in the 1960s. Nikon's standalone Speedlights (those not built into the company's cameras) have the SB- prefix as part of their model designation. Current Speedlights and other Nikon accessories make up part of Nikon's Creative Lighting System, which includes the Advanced Wireless Lighting, that enables various Nikon cameras to control multiple Nikon flash units in up to three separate controlled groups by sending encoded pre-flash signals to slave units.
Nikon competitors Canon and Ricoh use the similar name Speedlite for their flashes. Both names indicate that strobe flashes produce much shorter and more intense bursts of light than earlier photographic lighting systems, such as flashbulbs, or continuous lamps used in some studio situations.
Models Compatible with the Latest I-TTL System 
SB-400 Low-end lightweight unit (GN 69 ft, 21m @ 27mm)
Mid-range model - weighs approximately 300g without 4 AA batteries (GN 98 ft, 30m @ 35mm)
The Nikon SB-600 is a flash made by Nikon for their digital and film single-lens reflex cameras. The SB-600 can mount to any Nikon camera with a four-prong hotshoe. The SB-600 cannot control other flashes through a wireless connection, however a flash commander can control it wirelessly.
SB-700 Professional model - weighs approximately 360g without 4 AA batteries (GN 92 ft, 29m @ 35mm). Announced September 2010 and available since October 2010.
SB-800 Professional model - weighs approximately 350g without 4 or 5 AA batteries (optional fifth battery for quicker recycling) (GN 125 ft, 38m @ 35mm) (discontinued)
The Nikon SB-800 is a flash made by Nikon for their digital and film single-lens reflex cameras. It has electronic interfaces for through-the-lens (TTL) automatic exposure and automatic zoom to match lens focal lengths from 24 to 105 mm (35 mm equivalent), plus 14 and 17 mm with the use of the built-in diffuser or 14 mm with the external Nikon Diffusion Dome, as well as film speed in the range from ISO 3 to 8000 (25 through 1000 in TTL mode with film cameras). Its guide number is 38 meters / 125 feet at ISO 100 and 35 mm, with a maximum range of 58 m when adjusted at 105 mm. 
The SB-800 is part of Nikon's Creative Lighting System (CLS) and features the intelligent-TTL (i-TTL) exposure mode. With compatible SLR cameras (such as the D2H, D2X, D3, D40, D50, D60, D70, D80, D90, D200, D300/s and F6), it can be used as master commander as well as remote flash unit within a CLS wireless lighting setup.
SB-900 and SB-910 
SB-900 Professional model - released 30 June 2008, weighs approximately 415g. (GN 111 ft, 34m @ 35mm)
The Nikon SB-900 is a flash made by Nikon for their digital and film single-lens reflex cameras, released on June 30, 2008. It has electronic interfaces for through-the-lens (TTL) automatic exposure and automatic zoom to match lens focal lengths from 17 to 200 mm (35 mm equivalent) and 12 to 200 mm in Nikon DX Format.
The SB-900 is part of Nikon's Creative Lighting System (CLS) and features the intelligent-TTL (i-TTL) exposure mode. With compatible SLR cameras (such as the D40, D40x, D50, D60, D70, D70s, D80, D5000, D90, D200, D300, D700, D7000, D2h, D2hs, D2x, D2xs, D3, D3x and F6) can be used as master commander as well as remote flash unit within a CLS wireless lighting setup.
As of November 2011 the SB-900 was replaced by the SB-910.
SB-910 Professional model - announced 30 November 2011, released December 2011, weighs approximately 420g. (GN 111 ft, 34m @ 35mm)
Wireless accessories 
- R1C1 Wireless Close-Up System
- SB-R200 Wireless unit (GN 33 ft, 10m @ 24mm)
- SU-800 Wireless Commander - no flash, controls other speedlight units
- Wireless flash setup from momentcorp.com
- Flash products from Nikon USA
- Speedlight comparison chart from bythom.com
- Creative Lighting System overview
- Creative Lighting System review
- Overview and detailed description of all Flashes from SB20 - SB800
- Comparison: Nikon Speedlight SB-700 vs. Nikon Speedlight SB-600 review
- Nikon Speedlight SB-700 vs. SB-900: overheating (thermal cut-out) test
|Nikon DSLR and MILC timeline (comparison)|