I know this is going to sound gay, but please stick with me. Theirs a article in Mens Health about Ryan Reynolds and how he transformed his body from a skinny guy to how he looks today.
It goes into a hell of a lot of detail about getting the abs to show through and what sort of stuff he does to keep his stomach the way it is.
I know he uses a lot of boxing training (i.e Medicine ball, sit ups with belly shots and skipping) and it had a great diet plan accompanying it.
I'm no where near as clued up as most of the people posting in here but I'll have a dig around and try to find a link to it. One or two of the guys from my gym use it and they bulked up an toned in like 2 or 3 months.
The medicine ball got me my belly and I haven't had no complaints from my girl, but its not a 10 pack I myself am to lazy to follow it properly but I know its worked really well with everyone who has.
I hope its of use.
Edit: links:Diet plan
Edit: Its not the workout plan from the mag we've got but its pretty close...sorryWork out