[Jabbles]

Whenever I recommend Project Euler to people wishing to practise coding I always caveat it by saying "the first 50 problems are useful". After that Project Euler quickly becomes more mathematical, which is great if you wish to practise your maths skills, but may not be what you're looking for. There are exceptions, of course, and some questions may require implementing an important algorithm, but it is difficult to tell at first glance if you will be learning some esoteric area of number theory or something useful to your coding skills.

TopCoder, CodeChef, SPOJ may be what you're looking for.

(Having said that, PE is great fun if you're interested in maths per se).

[barkingllama]

Thanks for the advice... I was looking at the last pages and I've got no clue what's going on.

[HoLyVieR]

If your someone who isn't very experienced in mathematics, it's better to do them in order (easiest to harder) that's how your suppose to progress. If you're starting with the last one, it's normal you feel lost, it's like starting mountain climbing with the Mount Everest.