I have been asked to provide a self review including giving myself a numbered grade (1-5) for a multitude of areas based on "expected standards." Without having an explicit statement of the expected standards and little to no feedback for my tasks, I am having trouble rating myself. It is my thought to put down how I have demonstrated the specific attribute in the past but give no number. Any suggestions on how to approach this task would be greatly appreciated.

Just wiggle between 3 and 4
It sounds like you're in a really painfully bureaucratic and arse-covering organisation... my condolences. Assuming you can't get any useful guidance from your boss, I'd just semi-randomly assign 3s and 4s to everything. It's not a particularly honest path, necessarily, but these sorts of things are, in my opinion, in exactly the same vein as "giving feedback to your boss" -- fraught with landmines for the unwary. Just fudge it and get back to delivering results.
Follow the instructions and put a number.
If the format of the self-review requires a number rating, put a number rating. Leaving it blank is only going to bring you problems.
Assuming there are text areas where you can write about accomplishments, you are definitely on the right track by wanting to show real examples of how you have demonstrated those attributes in the past. That is a million times better than the generic bromides I see on most people's self-reviews. A lazy or simply overworked boss is going to rely heavily on what you've written when they do their part writing up your review, so make sure you are as thorough and exact as possible when talking about your accomplishments. If you have had areas where you've clearly made a mistake that will be remembered, briefly acknowledge it, but don't beat yourself up over it too much in the rating. Instead, write a sentence about how you learned from the mistake and changed your behavior to improve things going forward.
As to Matt's semi-random approach, here's how I would define semi-random: If you are truly a solid performer as compared to both your job description AND the performance of your peers as far as you can tell, make yourself average out to a 4, assuming 5 is the best (or a 2, if 1 is the best). Look through the categories, find about 20-30% that you consider yourself strong at and have lots of evidence to back it up, and give yourself the highest rating there. Find about 10%, or at least one category, that you know you are comparatively weaker in, and give yourself a 3 there. Everything else, put the next to best rating (a 2 or 4 depending on the direction of the scale).
My company gives some
My company gives some definitions of what 1-5 are, on our review (1 being low, 5 being high). For instance, a 4 is: Learns new tasks quickly with little supervision, often exceeds supervisor's expectations, carries out assignments in a superior manner, has potential for advancement and/or additional responsibility.
That's still got a lot of 'if' in it (what is 'little' supervision? Quickly by whose measure? If I don't know my supervisor's expectations in this area how can I know if I've exceed them?, etc.). I try to think like I was a boss reviewing someone else. (I never give myself a 5 or 1. And not really a 2 either.) If I was a boss, and I had to deal with me, would I be impressed with them occasionally - not just mildly pleased, but pleasantly surprised and/or impressed at how well they did in this area? Relieved because I had started getting pressure on something and they'd anticipated it and accounted for it in their work?
For example, for time management (sorry, priority management, but they call it time management on the review form...), if I got everything in on schedule, I'd put a 3. If my management had repeatedly told me 'the other guys said it would take 3 times as long as you did, so you did great getting it in on your schedule', I'd think about a 4. If I also always am late to meetings, I'd think about the 3 again.
Another thing I try to use as my evaluation criteria is results - how has my behavior with regards to that area done with regards to results? If I haven't gotten any feedback (positive, negative, or totally vague and ill-defined), the results question helps. One area there is collaboration. Collaboration is not something we're always told 'you gotta do this' (or rather, 'here's what we consider collaboration, do it'). So I try to remember, are there times I involved someone who I could have not involved but when I did, I got improved results over what I'd have gotten? (And I'm also defining results as '*later*, things went faster - not just the results now, as long as the results were good, but overall. Did me helping person X on project Y, when I didn't have to, make things better when we got to project Z and found ourselves *having* to work together?) That kind of thing.
Then I take my accomplishments for the year and put them into the text area to try to back up my numbers.
Preparing for YOUR review
By the way, have you listened to the "Preparing for YOUR Review" cast lately? Good info in there.