Ahhhh - corsets... yum!
Being a large girl I love what wearing a corset does for my figure. Having large breasts the waist cinchers are more practical for me rather than overbust corsets because they squish my tits up and give me a ledge to rest my chin on.. handy for a quick nap but not very sexy.
If you're pear shaped, most corsets will add cleavage as long as they're over the bust ones. Great things about a well-made corset is that they'll pull in the tummy and waist line as well.
Va va voooooooooom!
The best corset I've owned (and still do) is a Vollers corest. This is a UK company and they export all over.
http://www.vollerscorset.co.uk/homepage.html
A place in Australia which makes quite nice, not-so-expensive corsets (their quality has imporved way out of site in the 6 years they've been operating).
http://www.galleryserpentine.com/
My own personal advise would be to not buy a corset from a sex shop or anywhere that doesn't specialise in boned corsets. Alot of "corsets" that sex and lingerie shops sell aren't proper corsets. ie. they're not properly boned (have tacky plastic boning which just bend and don't hold) and won't shape your figure at all. If you're a skinny girl this might not matter but if you do want some constriction and shape you want proper boning.
I've seen a couple of gorgeous corsets over here from Stormy leather - ahh, if only I had the dollars. *drool*
As you're planning on losing weight go for a corset that would be suitable for the smaller waistline, the great thing about lacing is it allows for extra inches without ruining the look.
Some other sites which may help:
http://www.absolutecorsets.com/
http://www.meschantes.com/
Fabric corsets, especially in some of the brocades and velvets are just so yummy and elegant and can turn a simple skirt into an evening gown.
And! Another site with a stack of corset links:
http://www.victoriancorsets.de/corsets/links/links.htm
love to hear how you go!