Places to submit?

[Panky]

Use the default databases in popular submit tools. Default databases offer a good start. You can use the default database to help you find other sites as well.

Visit a few sites. Click on the trades/friends/recommended lists. Follow the links.

Use resources and directories such as;
The Links Machine
Porn Resource
Pimp Cafe
XBiz
GG&J

Visit popular TGP/MGP/Link list sites and/or niche specific TGP/MGP/Link list sites. Click on the galleries/freesites. Click on the recips. Follow the links.

Search using Google, Yahoo, MSN... Do exact searches, keyword/keyphrase searches, various combinations and spellings. Try something like boobs + TGP, boobs + thumbnail gallery post, (or whatever your niche may be),...

Watch the boards. People always announce when they are looking for trades, open for partner accounts, just launched a site...

Visit the script sites for popular TGP/MGP/link list scripts and traffic scripts. Some of those sites will have a list of which sites use their product.