I agree with link building through WordPress Theme sponsorship in 100%. Some days ago i mod free WordPress theme for my site, create a new one and use it there. After some time i decided to make it public and leave small link in footer with info that i’ve created it. Untill today i see incoming links in my WordPress panel. Also i saw many times on other people wotk that they creates themes for WP and then it gives to them many good links.
Dosh Dosh wrote a post about building lnk through Word Press Theme Sponsorship and ask question about is it good idea or not ?
Short part of the answer is:
If you submit your site to alot of directories it will improve your SERPs in the search engines.
Link populariy is a very big part of SEO. Using web directories is a great way to build more links and increase your site’s SERPs. People will not use web directories alot but spiders are. Spiders will still regularly index them and the links they contain. This is why submitting your site to web directories is still very usefull.
If you want to read more go here:
Why You Should Use Web Directories !