I bought a paper-making kit - but you don't really need to - the kit included the mesh frame you need for making the paper - and not much else really!
all you need is a frame (old picture frame) with something like net curtain stretched and tacked over it.
Paper shreddings are great for this - the result is a white speckled paper. But for these envelopes I used around 80% oak leaves - just scouped up off my lawn! I soaked them in boiling water for a few hours - then boiled them up in water for around an hour. this didn't seem to do too much apart from soften them. The boiling process is to break down the fibres to enable them to bind together when you make the paper. I then added a pile of paper shreddings as the oak leaves were very fibrous and I thought it needed something softer to help bind it all together.. The whole lot was then whizzed up in the blender until the leaves were fairly broken down - I picked out any stalky bits that didn't break down.
The resulting slop is then used to make the paper - I could talk you through it but it would take hours so probably best for you to google the method.
basically it is put into the mould - the water drains out through the mesh and you are left with a pulpy layer - this is the paper. I used an envelope shaped mould in the deckle (frame) so the shape for the envelope was already formed.
once you've made the paper and dried it - there you have them!
you can used any plant materials to make paper - I want to use nettles from my veg patch to make paper for seed packets to put the seeds in I harvest from my veg - a great circle of recycling! Ill have to wait until next year for that though!
seriously though - if you buy a papermaking kit - it is simple to make paper - these envelopes were the first thing I made - i tend to jump in!
this is the kit I bought - quite expensive but the materials you make the paper with are free so there are no more costs there.http://www.arnoldgrummer.com/product/paperMaking/productDetails.cfm?prod_id=24
I got it at my local art shop - this website is a US one just to show you the one I bought - it was expensive but its great quality and I wanted to be able to make an A4 sheet which this one does - you can seriously make your own mould though - i just didn't have the time/inclination! there are much much cheaper kits on the market.