Here's a updated list of new ongoing ctf challenges. Feel free for adding some sites!
- Root Me (Root-Me is a non-profit organization which goal is to promote the spread of knowledge related to hacking and information security)
- Pwnerrank
- Over The Wire
- WeChall
- Smash The Stack
- HachTheBox
- PicoCTF (A CTF for middle and high school students)
- CTFlearn (user-contributed challenges)
- Hacking-lab
- Enigma-Group
WebApp Specific:
Pwn Specific:
- pwnable.kr (all about pwning)
- pwnable.tw (new site for pwnable challenges)
Reverse Engineering Specific: