Tom,
We use the SCLogin module on this site. We have it configured for text links and have it set to the top module position on our site. You can likely do something similar with your template, but you'd need to integrate it into your styles as it wouldn't look exactly like your template by default.
Another option is to use the button type and have the module in the top right of your template. That will add a pretty blue "Login" button, and you can have it bring up a modal login view just like on this site.
I hope that helps get you started, but should you need anything else, just let me know.
Thanks,
Alex