I would wait at least until spring before planting in it. Un-composted cow manure is VERY strong stuff and it will not be good for your plants. Most likely it will burn them and they will die. I use cow manure in my beds after it has sat in a pile composting for at least a year. Once it has composted, you'll have a great planting bed.

MeMo

I agree with MeMo. As hard as it is, wait until spring. (I know that would drive me nuts :)
You do, indeed, have a great start there. You could have fun with this. Keep adding stuff for the rest of the season (look up threads about "lasagna gardening"), knowing that the more you add (compost, lawn clippings, shredded leaves), the better this bed will be in the spring. And having great soil right at the beginning will save you much work in future years.
Don't rototill too deeply (see soil food web threads in the Soil forum).
Do you have another bed where you can temporarily plant things that you might find in the end-of-season sales? That would give you a good jump on next season and help you plan this bed, too.

I wish I had an uncle with manure.

I have a new "empty" beds that I didn't put anything in this year - I have been trench composting our kitchen waste into them all summer. I throw a handful of dried grass or shredded office paper into the hole each time we bury stuff. I get coffee grounds from the convenience store around the corner and we produce a lot of corn cobs, melon rinds, egg shells, veggie waste. I embarrass my kids by bringing home food waste from picnics and such

I might plant a cover crop of sweet peas this fall, and turn it under to inject some nitrogen. My mother and I have big plans to collect and shred leaves from all of our family's yards this fall, and compost them in plastic bags.

It's hard not to plant stuff in empty dirt right away, but I am having a blast planning for next year. Just imagine how good our dirt will be, Missriss!

It's gonna kill me to not plant in this bed til spring!! But I kinda figured that would probably be best. I do have a bed that I affectionately labeled 'The Dump'. This is where I put things that I dig out and don't have a place for or things I buy and haven't figured out where to put them yet.

I have been reading up on the whole lasagna bed thing and really love the whole idea. Plus after reading a bunch of posts about composting and telling my DH about it he got into that and set up a compost bin last night. We used the wire circle thing and put the extra manure in so far. Since it's been so dry this summer there are already leaves that have fallen off the trees and I told him I can't wait to come out and rake them up to put in the bin or on the bed.

I agree with the others but there is no reason you can't assuage your garden urges with a few containers. You might even find a few perennials to plant there so they will get a head start for life out in the "real" garden next spring. While you are waiting for your compost to finish you can really concentrate on beautiful combinations in those pots and give them the extra care they demand.

Consider yourself extremely lucky that you are at least able to dig in your yard now -- mine is bone dry, cracked, and it would take a pick-axe to break the ground (no rain to speak of for two months now). Get your bed all set to plant next spring, manure definitely will burn your plants if it's too fresh! I have a pile my neighbor brought me this spring and hopefully we'll have some rain and I'll be able to work it into the ground...soon...