Bootcamp allow you to dual boot between Windows and Mac. Apparently, HFSExplorer recommended by a previous responder allow you to copy Mac files in HFS format to your Windows partition in HPFS format. However, if it's something you need to do often and you want a simpler & user-friendly solution, you may want to consider dumping the free Bootcamp and install a hypervisor like VMware Fusion. ( I understand Parallels for Mac, which is sold at the Apple Stores does something similar). I have VMware Fusion on my Macbook Pro for 4 years. VMware Fusion allows me to create a virtual PC on Mac OS X with a predefined maximum amount of disk space. It also allow me to determine how many processors (one or two on my Core 2 Duo MBP) and how much memory I want to allow Windows to use. I then installed Windows XP in this virtual machine. My Windows boot drive is saved as a file on my Mac. I configured the options so that this file is only as large as the files I installed in Windows, and it grows as needed as I install Windows programs and add data to Windows. My Windows boot disk is now backed up automatically by Time Machine when I back up my Mac. Each time I boot Windows when I'm in OS X, I have the option to change the number of processors (I can allow Windows to use all the processors in my Mac and it still works.) and memory for that one boot.
Now comes the part you are currently interested in. VMware allows me to designate Mac folders to be shared with my Windows virtual machine. Mac programs can operate on files generated by Windows in these shared folders, and Window programs can operate on files (e.g. mp3, jpegs, etc) placed in these folders by Mac programs. All the file format conversion is transparent.
Assuming I organize my folder according to my work projects, I can assign my work project as a shared folder in VMware. If I have a Microsoft doc file and I have Microsoft Office installed only in Windows and I do not have any program in OS X that reads .doc files, all I need to do to work on the Office document is to double-click on that file in OS X. This would cause VMware Fusion to start up, use the last established configuration, start Windows, start MS Office and open the document in its own window on my OS X desktop. This allow me to work with Mac files and MS Window files concurrently. Forgot if I ever copy & paste across OS X and Windows programs. Anyway, the interoperability is truly empowering.
Check it out.
I have used VMware Fusion on my MBP for 4 years and is very happy with the flexibility. Amazon sells a Version 2 for $19 but it appears to only support 32-bit OS X. They also sell Version 3 that apparently supports OS X in 64-bit mode and can run Windows in 64-bit mode. You will need to read the descriptions and customer reviews to decide which version you need.