I've just found a great and very extensive PDF guide to NDS Flashcarts and homebrew that has a wealth of information about every aspect of the subject.
The file was obtained from a site called http://www.moddz.com/ which is the website of a maxconsole member called FifthE1ement. He is currently in the process of updating the guide to include bit of more recent information, but on the whole the guide is already very useful as it is.
I would suggest keeping an eye on the maxconsole thread here for announcements about updates to this guide. Also post there to show your thanks if you find this guide of use.
To obtain the guide from his site you first need to register, otherwise you can't see the downloads area. But to simply things I have attached the PDF here for you all to download and read. Enjoy!
Hope this guide is useful for you Ghost.