How do I get the Android Kindle/nook apps to recognize .MOBI/.EPUB files on my SD card?

I prefer to manage my ebook files manually, so I'm having trouble getting the Android Kindle and nook apps to locate the .MOBI and .EPUB files that I put on my SD card. Is there any sort of Browse feature in these apps for locating custom ebook files? For the moment, I'm getting around this issue by using Calibre /FBReader , but I'd rather use plain drag & drop and the official Kindle/nook apps if possible.