A good running play I like to use is the Power O run in the Strong formation. Shift the linemen to "aggressive" or have them slide in the direction you are running. I got two 80 yard TD's with LT online (in one game) with this play. Watch the blocking, and I usually cut upfield in between the tackle and TE, or your FB makes a good block and you can go straight to the outside.
Also, try the plays in the I formation that the WR gets put in motion (green route on the play call menu) and again shift the line in the direction you are running. These tend to work well.
To perfect these plays, go into practice mode and use them against different defensive formations/plays. See what shifts should be made based on the formation of the D and make sure to throw in some play action online from these formations.