An awesome article from catswhocode with loads of great hints for WordPress theme developers.

Many WordPress Themes display post excerpts on blog homepage with a little thumbnail image of one of the images used within a post, but most of the WordPress themes I have seen, use some kind of external image resizing script like phpThumb or tinyThumb or they use some custom field in the post to show thumbnail image.

But WordPress has inbuilt functionality of generating thumbnails of the images you add to your post. This functionality is enabled by default unless you have explicitly set it from Media Settings in WordPress Settings panel.

predesigned comment themes for wordpress... just the comment bit.

Interesting article in the official wordpress codex with tips on how to release a theme to the wordpress community and the standards your theme should meet before being released.