I've just uploaded a new version of the visual studio addin for arduino that supports multiple sketch files in a single folder.
The ArduPilot project is a good example of this requirement.
It is very impressive to see all the hard work that has been invested in ArduPilot as Visual Studio intellisense 
Read more about ArduPilot in Visual Studio here Arduino Visual Studio - Multiple Sketch Project Intellisense
I installed the addin msi. I use Visual Studio 2010 RC. Does this work w/ 2010? I don't see it listed in the VS add-ins Manager.
thank you - this sounds very cool.
Sorry didn't see your post. There is now a 2010 version in the downloads area
i had some difficulties with arduino visual studio .i have installed and configuredvisual micro with these steps of the web site( www.visualmicro.com).when i compiled my program,the visual studio showed:
cannt findd:\VisualMicroforArduino\default_vsaddin_vsAddIn_build*.o
cannt find d:\Visual Micro for Arduino\default_vsaddin_vsAddIn_build*.a
cannt find d:\Visual Micro for Arduino\default_vsaddin_vsAddIn_build*.eep
cannt findd:\Visual Micro for Arduino\default_vsaddin_vsAddIn_build*.elf
cannt find d:\Visual Micro for Arduino\default_vsaddin_vsAddIn_build*.hex
avr-gcc: d:\Visual: No such file or directory
1>avr-gcc: no input files
1>Failed to create include_board.c.o (avr-gcc)
what's the matter? what should i do? 
I did reply to your message but it bounced back because i didn't use the forum
If you add questions to the vm forum instead of sending emails it is easier for me.
The errors you report are not errors they are just warnings you get the first time you compile.
The real error was at the end of the output and it showed that your avr folder had been specified incorrectly in the vs options. this needs to point to the avr BIn folder that contains the avr-g++.exe. you will find this folder below the arduino folder.
