Extreme Calisthenics/street abs&core workout with 10-15 killer exercises using a bar & bench. FB http://www.facebook.com/cwtraining - Great & effective routine/exercises using bodyweight only! List in video&description.

Front Lever raises/pulls
Dragon flag + Variations
Windshield Wipers
Clasp knife (sitting leg raise & crunch combination)
Toes to bar
Leaning crunches (hanging)
Oblique Crunches
Oblique Raises
Monkey Crunches
Side Raises
Sitting leg raises
Knee raises

I use to mix a couple of exercises for each target/involvement of the abs (not necessarily doing ALL these) working with both crunches and raises (straight and the sides) and also core to target all sections in a workout.

This workout is suitable for street/park/outdoor/home workout, a killer abs & core workout only using bodyweight! Find a bar or anything you can work with for the hanging exercises, also a bench or anything to sit on for those exercises.

Work with the form and step by step before going for the advanced exercises. Be careful with the neck doing the Dragon Flag, therefor its important you work up a good technique first.
To decrease the difficulty level a bit, work with one leg dragon flag, one leg raises etc. Then you can practise that before going for the full ones.

REMEMBER: No matter how good abs you might have you will not get visible ripped abs and the 6 pack abs until you actually work with a proper diet and reaching a lower body fat %.
Extreme ab training combined with eating clean and healthy, discipline with training AND food.

This is ONE of my videos in my Calisthenics / Extreme Bodyweight Training series.

Calisthenics INSPIRATION & MOTIVATION, Anytime & Anywhere:
https://www.youtube.com/watch?v=rI3FDVNeODU

See also the latest calisthenics workout routine (shoulders & triceps):
Calisthenics Shoulder & Tricep Street Workout (HD)
http://www.youtube.com/watch?v=rOJPTDxQfEw

and for more FULL WORKOUTS, see (for example):

Calisthenics & Street Workout - Summer 2013 (HD)
https://www.youtube.com/watch?v=whGRELIiHaM

Calisthenics: Street Workout 2013 (HD):
http://www.youtube.com/watch?v=zoWkSyS1Yf0

Calisthenics: Extreme Street & Gym Full Body Workout - HD.
http://www.youtube.com/watch?v=kzUcQM58kDY

My new Push up Movie: 10-15 Crazy Extreme Push Ups - Calisthenics Street Workout 2013
http://www.youtube.com/watch?v=naRaVsFn_g4