Can someone advise where the 1851-1855 City directories for Cincinatti are available?

The Cincinnati Public Library has a fabulous resource called the virtual library, where anyone can download books, music, maps, etc.
They have the images of Cincinnati city directories for most years between 1819 and 1894 online, you can download them as a PDF file.

Here is the link to the Virtual Library page:
http://virtuallibrary.cincinnatilibrary.org/virtuallibrary/

And then there is this site, there are other states on this one!
There are a bunch of Cincinnati directories, as well as other places, up on the Directory page:
http://directory.evendon.com

You can confine your search to the Cincinnati books using the SEARCH SELECTOR in the Left Pane. Or you can browse one book at a time by clicking on that book's link. When it loads, you will find links to all of the pages in the Left Pane. As you click on the link for a page, it loads in the
Center Pane. The Center Pane also includes links to step forward and backward one page at a time.

Don't be too trusting of the search index. It's pretty good but not perfect.

To view a list of material available click on "Browse Virtual Library". The directories are under "Downloadable City Directories".
There are also some books of genealogical interest under "Downloadable Old and Rare Books". They have the Cincinnati Sandborn maps for 1904-1917 online as well (under maps).

Hope this helps you,
Lori Deible Chaffin

Try this web site:

http://www.evendon.net/PGHLookups/DirM.htm

It has directories from 1819 to 1894.