more resources and suggested collabrative software application

http://www.photoshoproadmap.com/
some tutorials for photoshop

http://www.adobe.com/

the official website for Adobe programmes including photoshop

For question number five :
suggested collabrative software application :

http://picasa.google.com/
this programe can edit photos and effects to them

http://www.gimp.org/
this programe is similar to the photoshop and it can be replacement for it . It can edit photos and retouch them digitaly