PS. modification...I just noticed that I'm referring to picasaweb.google.com, not picasa,
in case there is a difference for you...Picasa is a computer program to store, organize and modify pictures on your computer. Imageshack and picasaweb are both online websites for photo storage.
Picasa does make it very very easy to upload your pictures to picasaweb.google.com. Much nicer than ImageShack, IMO.
Johnny, when looking at your pic in picasaweb, over on the right side there is a link and "embed image" option. You can choose the size to embed as well. It is way easy.
Just choose your size, check the "hide album link" box, and copy the text and paste it in your post.