Err....I guess this aint correct place to ask this question... But i couldn't find any place where i could get the desired coding problems, that i should put up in a Coding contest, which we are organizing as a part of our college function & I really want the Problems to be Advanced!
If this is a college-level contest, take a look at the problems at UVA Online Judge.
You should try searching http://www.acmicpc.org
The past world finals problems are there and if you search there you will also find past regional and world finals question sets.
There are books and books of such problems. However, remember that the contestants are also looking at such resources, so if you use a question from one of them, some teams may have an advantage of having already solved the problem...
If it is not a contest for beginners, I would recommend not getting the problems from any well known website/online-judge/contest. Any serious contestant usually practices problems online and is well aware of all well-known sources. It would be like knowing the questions of an exam for him/her.
For local university/school-level contests in our region, we generally come up with original problems. A good idea for you would be to contact former contestants (e.g. ACM ICPC contestants) from your locality and invite them as volunteers to contribute problems.
I have a list of these sites on my blog post Programming and Logic Puzzles along with a short explanation of the kinds of problems you'll find at each site.
Formulating the questions with your own knowledge seems to be a good option. Search the net for some hints, but dont copy-paste them as they are.