It all depends on the directory and it's submission guidelines. On my
PC Property Manager site the
property investment directory is managed as a quite separate entity and some directory owners will allow me to submit it. Others won't.
Directories can also get a bit fussy about listing other directories (ie competition) and that may be your bigger problem.
However I do hit restrictions with my
Simple SEO blog which I tend to promote over the actual index page because a) it's a sub-folder; and b) it's a subdomain - but lots allow it too.
Good luck!