Here are some interesting sites from rescol for you to understand the time in English.

To revise it from clocks to digitals :

Teaching Clock
" This clock will allow you to change the time in whatever minute/hour intervals you want."
(time-for-time.com)

Telling Time (harcourtschool.com)

To learn :

http://www.britishcouncil.org/kids-flashcards.htm

TIME
Print flashcards.

The time 1 (142KB)

The time 2 (143KB)

The time 3 (138KB)

To practise :

Hot Potatoes Exercises : Time (benedicte.mallet.free.fr)

Learning to Tell Time - with explanations and short interactive exercises (arcytech.org)

with sound :

Time and Daily Routine - Interactive Book
(Laurence HAQUET - Ac. Rouen)

TIME! - Exercices interactifs
PART 1 : Numbers (page 3) / PART 2 : Time! (page 11)
(Josiane Behengaray - Ac. Rouen)

The Time - avec animations et son