Integrating VoIP into application

Hi

We are wanting to develop a system which allows for multipoint conferencing over the internet using VoIP- i.e. allows 3 or more users to communicate with each other at the same time.

Our whole development team are information systems students, not computer science students. Thus we would really battle with the nitty gritty of programming a VoIP application from the bottom up.

Now, what we are looking for is a developers toolkit, which would incorporate all the low level programming and make it much easier for us to create a system using VoIP. We have the following criteria:

1. We would ideally like to develop the application in a .NET language, but might have to settle for C++, Delphi or Java.

2. We don't have too much money to spend.

3. We would like to use either the H.323 or SIP protocol. Those seem to be the main ones.

We have done a lot of searching and have not found anything ideal yet. Any ideas as to what we could use?

Many thanks in advance

langals