I know the AMCAS does not open up until May, but are there any reliable sites or resources that would allow me to start the process on my own and simply transfer it to the application when it is time??
Sure, you can prewrite your personal statement and activities section, assuming the format doesn't drastically change next year. If you google "2014 AMCAS instruction manual" and go to the first link, you'll get the entire detailed instructions for writing each section - things like character limits and tips.
I concur that the PS and some compilation of dates and short essays for the activities section is all you should worry about now. Especially the PS. Get several people to go over it and be ready to write a handful of drafts.
You may want to think about and start drafting the personal statement and "most meaningful" activities sections in a word document. Other than that and asking for LORs, there's not much else that can be done this early.
Don't forget about letters of recommendations! Make sure you ask for those early. Although you don't need them to submit your primary, most schools won't review your secondaries until you submit your letters. I failed on that front and had to complete my secondaries rather late in the cycle.
Pre-write all of your activities and write your personal statement. Also order your official transcripts from all institutions attended to use for reporting your grades on the AMCAS application. Collect recommendation letters from professors using Interfolio. Once you have all of this together, filling out the actual AMCAS in May will not be very difficult.
If you are really trying to get on top of things, and you know what schools you are planning to apply to, you can also look up what each school's prompts were from last year to get an idea of what sort of secondary essays you should write.