By default the stock osCommerce code is not really optimized at all. One contribution I have found useful is the “Really Easy HTML Title” contribution. The main downside to this is that you have to edit files manually to use it but you really only need to edit two files, the main ones: index.php and product_info.php. The rest are ok to edit but those two files take care of the main page, the product category page, and the product page itself. After the contribution is installed the page names will look like this:
Store Name – Category Name – Product Name
In the SEO arena every little bit helps and this contribution definitely fixes up the title tag.