The Hadouken is the signature move of Ryu and of fighting games in general. Ryu gathers Chi into an energy ball and releases that energy towards an opponent. Ryu had this capability in the original Street Fighter I game and has had it in every appearance. When Ken was altered to play slightly differently than Ryu, Ryu was given a more powerfull Hadouken than Ken, while Ken was given a more powerfull Shoryuken. This move is always performed with QCF+P. The higher the strength of the punch button pressed, the faster the hadouken travels across the screen. The Hadouken is about half the size of a Ryu and is released at chest-level. The Shinku Hadouken is a super-version of this move.
Shakunetsu Hadouken (Red Fireball)
In Super Street Fighter 2 Turbo, Ryu gained a slower, more powerfull, and red version of the Hadouken. The move re-appears in several games but most noticeably does not appear in the Street Fighter Alpha Series, presumably because he did not learn this move yet. In SSF2T and Capcom vs. SNK 2, this move can be done by doing a half circle instead of a quarter circle forward (HCF+P). In Street Fighter 3: Third Strike, Ryu can perform a similar red fireball (the EX version of the Hadouken, consumes energy) by pressing two punch buttons at the same time while performing a normal Hadouken. This move can also knock down an opponent.
Shoryuken (Dragon Punch)
Ryu and Ken have had had the Shoryuken move since Street Fighter I. It is a rising dragon uppercut attack which moves slightly forwards (though not as forwards as Ken's would later do). This move eventually became Ken's signature move and Ryu was given a less powerfull version of the attack. The EX version of this move in Street Fighter 3: Third Strike happens when two punches are pressed at the same time while executing the move, hits twice when starting from the ground, and has a faster startup. Unlike Ken, Ryu does not commonly have a suped-up version of this move, although he can perform a Shin Shoryuken if powered up at level 3 in Capcom vs SNK 2.
Tatsumaki Senpukyaku (Hurricane Kick)
The Tatsumaki Senpukyaku is the third basic move characteristic of the Shotokan style of martial arts. Ryu leaps straight in the air with one leg while the other spins around in a fierce hurricane kick. While spinning, Ryu travels horizontally forwards across the screen. In some games, this can be performed while in the air. The "Shinkuu Tatsumaki Senpuu Kyaku" is a super-version of this move.
Joudan Sokotou Geri
In the Street Fighter 3 Series of games, Ryu has a special forwards sidekick that sends his opponent flying. It is performed with HCF+K. The EX version (consumes energy meter) bounces your opponent off of the wall for a juggling opportunity.