Well, I don't claim to be an expert, but I've done
most of my cels in frames, so here's my
experience.  (This is gonna be long winded so
brace yourself)

1.  For materials this will be a mix of things. 
For most of it, it'll be stuff you can obtain
online, but some of it you'll need to get in a
store.  

If you're planning to cut the mats and stuff,
first you'll need to get a mat cutting "board." 
These can range from $20-$60 for varioustypes. 
The one I have is a Logan Craft and Hobby
Matcutter.  (Includes a cutting board for up to 30
some inches, a guidebar, and two types of cutting
tools)  You can get this at most Michaels for
around $50 (check out the ads for a 20% of 1 item
coupon that seems to happen every week).  It's
served me well, though I tend to cut a bit deep in
my mats and always need to replace the bottom
"guard" mat for the cutting board.

Depending on the glass you're using, the location
will vary depending what you're using.  If you're
using glass, I find the only place to find UV
conservation non-glare glass is an artshop such as
Michael's or Hobby Lobby.  Not too bad at $10 for
an 11 x 14 sheet, though I wish I could find
something better in my area.  If you're looking
for plexiglass, I believe you can find online stores
that'll cut and sell sheets of them.

For frames and foam backingboard, you can find a
lot of frame places online that will custom cut
those self-assemble metal frames.  If you're
looking for wood (which is more expensive) some
places have those as well, though I'd go to a
artshop / framer place to check it out if you have
an intricate pattern you're interested in.  For
the really cheap, yet very useful metal frames I
go to "Frames by Mail" (www.framesbymail.com). 
They work well for small frames (had no problems
with 12 frames), but I've heard they have trouble
with excessively large sizes.  A more reputable
places I believe is "American Frame" (sorry don't
know the site but it should be easy to
google-smack).  I believe both places offer
acidfree foam backing board that can be cut to
your frame specs as well.

Mats are another story.  Unless you're going the
route of single color mats (which i'm doing for
the moment) you'll have to get these in art
stores.  (Online salers seem to sell in bulk only
of 12 sheets of 54 x60 or such per order)  You can
get these at the same art store you get your glass
at.  Be careful, even for nice ones, mats are
usually around $2-5 per 11 x 14 sheet.  (I once
went to a Michael's that tried to massively
overcharge me, 3 sheets of 11 x 14 mats almost
cost me as much as 3 panes of non-glare UV
conservation glass!)

A final thing that might be used as supplies is
acid free foamboard / matboard (sometimes called
museum rag I think?  But it's basically really
thick paper) I use this to float the cels within
the frame by cutting these like mats and
sandwiching the cels in between.  Don't know if
you can find these online, but they're readily
available and pretty cheap in most art / hobby shops.

I think that's about it for supplies.  If you have
any more questions feel free to email me.  Oh,
while not a specific material, I find it useful to
have a can of compressed air.  It's great for
blowing off particles on glass (particularly if
its on your UV coating) or if you like using
textured mats, it greatly helps cleaning off the
shavings after cutting.

**An important note about supplies.  Make sure you
estimate correctly about the amount of materials
you're using.  This will be critical in determing
the thickiness you need for the frame.  (In fact
it's better to overestimate than underestimate) If
you find that you have more materials than the
frame can hold, you're in for some trouble if you
ordered in bulk.  13/32 of an inch is probably the
very smallest you'll want to go.  It'll allow for
the foam backboard, the glass, 1 mat, and a sheet
of board to float the cel.  (I originally ordered
in 13/32 and now am slowing replacing for larger,
probably 1/2 inch or more to have more play with
the mats. )

2.  I'm not an expert for line fading, (in fact
I'm usually stumped by the exact cause of it) but
I try to adher to basic cel care guidelines.  In
addition to the UV conservation glass (a definite
need in my opinion), I keep my cels away from high
humidity (bathrooms), high heat (heater vents),
and direct sunlight.  Some people say it's good to
"air" out the cels after a couple years and to
replace the mating and materials as it's lost it's
neutral balance, but I haven't had my cels framed
that long  yet.  I'll probably do it anyways to
play with styles and keep my skills up so I'll
probably never   really know if it helps.

3.  The best way to hold a cel in a frame is to
sandwich it between mats and to "lock" it in place
using acid free tape.  (Can be found just about
anywhere)  Once you place your cel down, you can
attach two small piece of tape to the corners or
upper edge of the cel.  If you're lucky, some cels
have some acid-free tape there already from being
attached to a background.  Those times I just
attach the tape to those connections points.  

4.  Types of boards?  Well acid-free is the
recurring trend here.  I like the alpha bainbridge
suede mats for display becuase they have a nice
texture to the front.  Makes a neat little effect
when you're up close. It'll all depend on your
style.  

For general notes, basic framing isn't that hard
at all.  It's like any skill, it takes some time
and some patience to pick up. (Double-triple
mating with designs and flairs are a bit more work
and practice) But, if you're willing to expend the
effort, I don't see why you need to go to a
professional framer which costs 5-10 times self
framing.  If you do go professional, be careful
where you take it to.  I've heard horror stories
of ruined cels that were cropped or dry mounted. 
Make sure the framer knows how to handle the cel
first.  

Oh, a nice starter website to help you on your way
is Kenneth Allred's.  

http://users.animanga.com/kallred/FrameIt.html 

It's a great page that uses animated gifs to help
you figure out the process.  As you frame more and
more yourself, you'll add your own little tweaks,
but this gets the basics down very well.

Anyways, good luck to you, and hope you find joy
in showing love to your cels by framing them yourself.

Howard