I like most (if not all) of the rider music I've heard, but these are my favourites:

Theme Songs:
http://www.youtube.com/watch?v=QEP4VFyzAF4
WBX (Double)

http://www.youtube.com/watch?v=8zladOg3q6g
Climax Jump (Den-Liner Form) (Den-O)

http://www.youtube.com/watch?v=IQ6yJXe-A7g
Anything Goes (OOO)

Other Songs:
http://www.youtube.com/watch?v=lrl-tdq_bDI
Power To Tearer (OOO)

http://www.youtube.com/watch?v=G8vGf42HKR4
Take it a Try (Blade)

http://www.youtube.com/watch?v=lEekf9WtVcA
Missing Piece (Wizard)

How could I ever forget one of the best fight songs ever?

http://www.youtube.com/watch?v=tnQurrST5VY

Kamen Rider Black Ending - Long long ago 20th Century

Kamen Rider Black RX Insert Song - Warrior of Fate (Unmei no Senshi)

Kamen Rider Shin Ending - Forever

Kamen Rider Agito Ending 1 - Believe Yourself

Kamen Rider Ryuki Ending 1 - Endless Life (Hatenaki Inochi)

Kamen Rider Blade Opening 1 - Blade Brave

Kamen Rider Kabuto Opening 1 - Next Level

Kamen Rider Kabuto Ending 2 - Lord of the Speed

Kamen Rider Den-O OST - Ore! Sanjou!

Kamen Rider Kiva Ending 1 - Destiny's Play

Kamen Rider Kiva Ending 2 - Supernova

Kamen Rider W Cyclone Joker Ending - Cyclone Effect

Kamen Rider Fourze Ending - Giant Step

Kamen Rider Fourze Insert Song / Kamen Rider Climax Heroes Fourze Theme - Endless Play

Kamen Rider Wizard Flame Style Theme - Last Engage

Kamen Rider Gaim Opening - Just Live More

Whenever I hear "Believe Yourself", "Gotta Keep It Real", "Shout Out", and "Cyclone Effect", I get the urge to fight. Likewise certain songs by the Kamen Rider Girls.

Voyagers by Anna Tsuchia:

http://www.youtube.com/watch?v=A6GRCqSqSOA