excel2latex; I'm not sure how well it works, but it's on CTAN.
If this or some similar program doesn't work, and it is absolutely, positively not an option to recreate these tables in LaTeX, the best you'll probably be able to manage is convert them to an image and include them that way.
It seems that there are some convoluted ways to do this from within Excel (see, e.g., convert MS tables to images.
You can also simply take screenshots and get the images that way.
You can then include the resulting image in your LaTeX document in the usual way:
The problem with this approach is that your fonts, line thickness, and such may not match those in your tables. But that is a peril of using binary or non-transparent file formats.