Summary of contributions for reference letters Pretty much all the profs I'm asking for a letter from I've done a fair amount of research under. However, I haven't spoken to a couple of these profs for a few of months and considering how busy they are I wouldn't be surprised if they've mostly forgotten about the specifics of what I did. So I thought it might be a good idea to attach a document summarizing my work with them when I ask for a letter, and I found a couple of other sites that suggested doing the same thing.

For this document, I was wondering if it would be a better idea to give a detailed page or so long description of everything I did or 5-6 bullet points summarizing my main contributions. The obvious benefit of the former is that I get to remind them of the details of everything I did, but it comes at the risk of them not wanting to read so much and pretty much ignoring the document.

For people who have done this in the past/planning on doing this now, what does your summary's format look like and how long/detailed is it?
There is no reason, actually, not to do both. What you suggest is very likely a good thing and will save the writers a bit of time. But you can have a bullet pointed introduction followed by a longer description of the work. Make sure the second part is labelled as such. If the prof's memory is jogged by the first part they have no need to keep reading. Otherwise they may appreciate it. 

You could even use wording that they might want to copy into a recommending letter. Make their life easy.