Pronunciation

Good pronunciation channels:

Christina Rebuffet - some videos on pronunciation - fab!
https://www.youtube.com/channel/UCtWyH1MB_A3OggdzoGtkeQA

 engvid
http://www.engvid.com/english-lessons/ - choose the pronunciation ones

Oxford Online English  -
https://www.youtube.com/playlist?list=PLD6t6ckHsrubLp8Ia8duzu5fN4riM2-Bl

Rachel's English - American, but very useful and good stuff!
https://www.youtube.com/channel/UCvn_XCl_mgQmt3sD753zdJA

engfluent (two videos on pronunciation to date, but more on listening, etc)
https://www.youtube.com/playlist?list=PLiDuxHgWdcgyGRifUg0RaFG6Q1CPG1XrT

Doing English with Julian - long and blah blah but good advice on how to become more fluent
https://www.youtube.com/user/doingenglishDOTcom

PRONUNCIATION: S vs SH sound

Algunos de vosotros tenéis problemas para distinguir o hacer el sonido de she, shhhhh!  y os sale una s

fijaros que no es lo mismo decir :

short que sort
Sue que shoe


Here is a few podcasts and videos to practise the shhhh sound

http://www.engvid.com/english-pronunciation-s-sh/

http://www.bbc.co.uk/worldservice/learningenglish/grammar/pron/sounds/con_voiceless_8.shtml


The one below...este os da vocabulario y expresiones con el shhh sound:
It's vaughan giving words with this sound. He doesn't compare it with s sound, though.
Your problem seems to be that the you produce s in situations where you should say sh

http://www.ivoox.com/pronunciation-of-the-sh-in-english-audios-mp3_rf_1652032_1.html
Enjoy