If you're using either a PC or a Mac computer, try Send to Kindle:
http://www.amazon.com/gp/sendtokindle/pc
I find it more convenient than e-mailing. This may not be relevant for you, but what I also like is that it gives you a choice as to which of your Kindle devices to send to and whether you wish to store a specific document in the cloud or not (you'd probably want to, for the synchronising, but sometimes there might be no need for a specific document or ebook).