A wonderfully simple site. Try it; you'll like it.
<> - Phonetics- The Sounds
of Spoken Language : A super-comprehensive site (which I learnt about
from Caroline Gwatkin), where you can see how each sound is articulated
(animated diagram + video) and hear a few samples (American English,
Spanish and German). You can also try their "interactive diagram of
articulatory anatomy" (available in English and Spanish).
< > -
Learning English - Pronunciation Tips - On this site (which Barbara
Chap, a dear Webhead, once recommended) you can discover phonetic
symbols (downloadable posters available!), enjoy 3 radio programmes on
the topic (plus try exercises and tapescript!), test your hearing with
some minimal pairs, and go on to learn about the relationship between
sound and spelling, schwa and discover the complexities of connected
speech. All exercises and recordings are downloadable, and therefore can
be exploited offline!

A lot more specific, but perhaps of interest to some of our learners
(from a link recently reviewed by Larry): a podcast on the pronunciation
of irregular verbs:
  • Listen in pop-up window:
  • Download (Right-click or option-click the link):
<> (836 Kb)

Background music and rhythm turn this exercise into an enjoyable chant!
[:p] Three other lists are also available.

Finally, don't miss our own collection of sites on pronunciation: