The biggest problem I've had in trying to get into women's clothes is that men's bodies are just proportioned differently. Where this makes the biggest difference is across the shoulders. Getting a dress that fits approximately right there means something for a seriously obese midsection. Multiply this problem by ten if you are at all athletic in the arms, chest and shoulders.

So your choices will likely involve either some alterations, or some consciously baggy styles.

I have a very baggy, shapeless but short black sequined number that works perfectly as a sort of Judy/Liza at her most out of control thing. I think I look fabulous in it -- but then I'm going for "funny" not "lovely". If you're more serious than that, you may need to find an open-minded tailor or learn to do some basic taking-in sewing.

I second Matt's advice: suck it up and try stuff on at Goodwill. Yes, you will be publicly outing yourself as a pervert, but seriously, who cares? It's not like you'll be surrounded by coworkers there. And you're unlikely to be the weirdest thing any given Goodwill or VV has seen in any particular day. If have a friend who can go with you, the embarrassment might be lessened -- plus they can tell you how things really fit in places you can't see.

This might help:
http://www.womenssizechart.com/

Looks like you may be a 3x/4x or 28. :-)

Look online for tall women stores and I would say a size 3x would-be good

Women's sizing is not consistent from brand to brand, period. Weight is not a good indicator of size for women's clothing, either. You have to worry about measurements at shoulders, bust, waist and hips and how the garment is cut (empire waist, natural waist, drop waist/ fitted bust, loose bust, built-in cups/fitted hip, a-line, etc.). Your best bet is to shop online and have your measurements (bust- widest part of your chest underneath your arms, waist- thinnest part of your middle, and hips-widest part of your hip around your behind) to compare to measurements for each article of clothing. You're going to want to buy almost-shapeless clothing (nothing fitted!), because your body's contours are not going to be like a woman's curves. Maybe a halter top or a top with a yoke that just goes around your neck but doesn't have shoulders and is loose from the bust down to accommodate your shape would be best. I'd worry about fitting your chest and shoulders and making sure the dress is long enough, then buy a large belt to cinch the garment around your waist. While I can't tell you a specific size, I can pretty much guarantee that you're going to be an XX+, and you should probably try to shop at/with stores geared toward plus-sizes (Lane Bryant, Fashion Bug, etc.). It's hard enough, though, for women who are within sort of "standard" sizes and who have been buying their own clothes forever to find clothing that fits, so hang in there, it might be a pretty long search.

It probably depends on the cut of the garment and the fabric being used, but you are most likely size 24-26 or so. Matt is right though that not all size 24s are the same! It is crazy! You should know a few other things too...one is that you will probably need to look for size 3x or so...maybe even 2x in addition to size 24. They have the two different ways of denoting size generally. If you are buying online, almost always they will have a size chart that shows inches or cm in relation to how that company sizes things. Also, many companies have an average cut and also petite and tall cuts. Go for the tall if you can find it, because average usually conforms to a person who is about 5ft. 6in. from what I've found, and you will find if you get the tall cut the sleeves will fit better as well the length of the dress will be more accurate. Most companies also fit for an hourglass shape, so if you have a non-hourglass shape you might have to size up or down or get the dress altered so it fits better. Some companies, like torrid, tend to size things more snug and others are more loose, so you kind of just have to learn by trial and error with that. Hope this helps a bit.

It depends on the garment. Some are sized best by chest size, some by waist size. Unless you upsize, you're going to find things horrifically tight across the shoulders and upper back and way too short.

You're built much like my husband (you could probably wear each other's clothes), and the only way you're going to find tops that don't impede your arm movement is by buying at least a 3X. The sleeves will be too short, unless you can find talls, but even the talls for women are meant for women 3 inches shorter than you are.

Skirts will be easier; they're going to be sized by waist. But they'll want to fall off, since your hips and butt probably aren't that much bigger than your waist. And they'll be short, unless you buy church-lady ankle-length skirts.

Big guys kind of have to wear sack-shaped women's clothes. Fitted stuff is definitely going to be out.