*.php to *.html

//Change File extensions 
for file in *.php ; do mv $file `echo $file | sed 's/\(.*\.\)php/\1html/'` ; done


//Rename all folders and files to lowercase on Linux
First, make sure zmv is loaded.
autoload -U zmv
Also, make sure extendedglob is on:
setopt extendedglob
Then use:
zmv '(**/)(*)~CVS~**/CVS' '${1}${(L)2}'

To recursively lowercase files and directories where the name is not CVS.