My first suggestion: Create a folder on your computer just for your cosmetic chemistry recipes. I've taken this a step further and I have sub-folders for different product types or things I've researched so I can find them quickly. If you're the type who downloads things from manufacturer's sites, rename them to something you'll actually understand (instead of the numbered ones I get from most sites).
As a note, don't bookmark sites because they can go away (try finding something on Martha Stewart you loved 6 months ago!). Save the page somewhere. If you're a Mac user, turn it into a PDF by choosing "file" then "print" then print to PDF and save it as something you will remember. I have no idea how to do this on a PC, but you can copy the text and save it in a text file somewhere. (Macs have PDF printing built in. I haven't used a PC in years, so I have no idea if they do this now.)
So for instance, I'm trying to get back to the challenge posted in December 2009 for the shower jellies (duplicating Lush), so I wrote down all the notes I'll need in the workshop for working with carageenan, details on the various surfactants I could use, and other things I might find useful. On the right hand side, I've written what I'm going to try at the top, then my notes on what I actually did as you go down the page.
When I'm done formulating for the morning, I'll come into the computer room and type up the recipe so I have it permanently. (I have lost notebooks before and it's a catastrophic event!) Then I print it!
My third suggestion: Keep a binder with tried and true recipes. (I have a binder with my usual recipes, another with mineral make-up recipes, and a third for potential recipes I want to try from manufacturers. You don't need to be this compulsive!) I put the recipes into plastic sheet covers because I can write on those with a grease pencil (sometimes called a China marker) or with a dry erase pen as I'm going along, even if I've made the recipe a hundred times. (This is useful for ticking off when you've included an ingredient or for doing the math to make larger batches.) If I make a change I really like, I pull out the sheet and make a note on it or I might type it on the recipe sheet and re-print it. And yes, get those tabbed dividers because eventually you'll have tons of different categories and you don't want to look at every page to find the shampoo recipe you want!
If you're also doing research, I suggest going for smaller notebooks rather than larger ones. I realize a 300 page book is a better deal than my favourite 80 page graph paper ones, but I can have a book for each topic instead of trying to remember where I put that information on lanolin. I know it's in the oils notebook (and yes, I have something like four of those!) Or make sure you use those tab dividers in a binder so you have an idea of where everything might be found!
I realize this all sounds very obsessive compulsive, but it's the only way I find I can keep everything in order. I love my computer, but there is always a chance she could have some hardware malfunction and I could lose all my precious recipes and writing, so having a paper copy is a great way to ensure you always have something on hand! (As well, what happens if the 'net goes down! Oh no!)