T309 (1994-1996)
The original badass debuted with a carbed 855cc mill straight out of Triumph's sportbike, the Daytona. Corralling the 98 HP motor was a steel backbone frame, adjustable suspension and dual front discs. Power was big and so was the weight, but nobody cared. It was the closest thing to a streetfighter any factory had ever produced.
T509 (1997-1998)
The second generation Speed Triple introduced the infamous "bug-eyed" look and the equally defining single-sided swingarm. Though displacement was unchanged, the Triple now used Sagem fuel injection and pumped out 108 HP. Two steps forward and one step back though: power was up and the handling improved, but the temperamental F/I hurt performance.
T595 (1999-2004)
The third installment gave the Speed Triple the Daytona's 955cc engine with far more power than previous models. Little changed in the way of aesthetics from the T509. Then, in 2000 Triumph labeled the Speed Triple the "955i" to let the public know they were far different from the similar looking T509. Little changed, save for a murdered out Special Edition in '04.
1050 (2005-Present)
A totally new bike was introduced. A 1050cc, 129 HP motor came with radial brakes, inverted forks, Keihin fuel injection and a new dash. Consider it social distortion on two wheels.