Help with best compression for web based showreel.....

I am a cinematographer who is having their first website built. My webbuilder has asked me to give them all of my files which are commercials, music videos and shorts in small files that can be up loaded easily. I have searched the web but it seems difficult to find information as to which is the best way to go. I have access to Adobe Media Encoder and it seems that H264 is the best codec. My original files range from Quicktimes that range from 80-5GB in size (1280x720 pixels) and standard files (1024x576) and clips in a native resolution of (720x576).

My question is should I encode these files all to 720 x 576 in the quicktime preset and using the H264 codec or should I convert using H264 as the format itself or should I be using Flash encoding as that is how the website will be showing the spots,I want to keep the quality at its highest.. also is there an optimum size of file that will stream well... sorry I a newbie when it comes to technical stuff regarding compression...

Any help most appreciated...


Hamish