Here's the links for the IR hosts named above,
LAConvolver for the Mac
Kefir for the PC
Voxengo Boogex for the PC
Freeverb 3 for the PC
For Impulse Responses I thoroughly recommend Recabinet located here:-
I use this for all my IR's and they sound great and are very professionally produced. For free IR's try the demo version of Recabinet or try:-
Here you'll find loads of advice and IR's for use with all the above hosts.
Finally, I'd just like to say that I don't use any of the above software but have some experience with LAconvolver, so I'll be useless for technical support. Please use the help provided with the programs as I won't be able to offer you advice or support on how they function. If you require help with Space Designer or LAconvolver feel free to ask!
Hope you enjoy recording in this way and I'll see you next month for more playing over changes!