I've haven't played Orks in something like eight years, and even then not with my own army, so I've put this little list together based on what I've seen of Orks from the opposing side. I've gone for a primarily close combat force because off the top of my head I don't remember losing more than a few Eldar to Ork shooting.
Basic modus operandi is; Boss, nobz and boyz get to the enemy asap and stab them in the face. Grots hide in a table corner somewhere. Deff koptas try and take enemy vehicles roughly from behind, Deff Dread supports the assault.
As I said I'm a complete newbie to Orks and this is just a small army to test things out, so any advice welcome.
Warboss Bullfrogg 'eavy-armour, power klaw, shoota-rokkit, boss pole.
5 Nobz eavy armour, big choppas, waaagh banner, stikkbombz
20 boyz stikkbombz, Nob, big choppa 'eavy armour
10 Gretchin w runtherd
3 Deffkoptas, buzzsaws
Deff Dread w DCCW, rokkit launcher. Grot riggers
Total: 750.