you can build a good data acqusition system using PIC18F4550 micrcontroller, this MCU contain 16 channel 10 bit A/D with maximum sampling rate 102 KHz and build in USB interface, the PIC USB firmware you will find it for free on
www.microchip.com, try CDC firmware cause it emulates COM ports through USB which mean you can any simple software to interface it as real serial COM port like C/C++/BASIC/MATLAB/LabView.
if you interested in C++ then you will be able to build your DAQ software, with some other DLL's and libraries you will find it for free on the web then you will be able to build a very good software, also you can use Visual BASIC instead of C++ its good choice too.
Or you can build your DAQ card using discrete components like FTDI USB interface chips and A/D
chip, the software you can build using C++ or Visual BASIC.
otherwise use Labview, i know its not free but student version only with 80$ i think.
good luck