This is a lovely looking site. Shows very well how it's possible to get lots of information in a page yet still leave it looking clean and crisp. I especially like the link menu. Soooo many people go for image links or java/flash links to make it look good when just a bit of time and patience can make a normal text link menu look so damn good!!
Well done...
Couple of general comments about site layout....
Not 100% certain about the business directory having main headings at Right...quirky but not notmal. Takes some getting used to which isn't what yuo want with directories. Your eye needs to focus on top headings and then move to sub headings which is naturally left to right.
Is it possible to make your link boxes smaller so you can have a bigger main content window as this is the theme of the site. I know the Business Directory is a long word but even a few characters makes the difference...
I am mentioning this but not sure if ti's valid. There is nothing that actually says what your site is for? I worked it out beacuase I browsed it but not obvious to the first user. They may see it as complex to understand. Ok ok it's called home assistant so the business directory naturally is full of things for home assistant but can you afford to assume that your users will pick that up in the first 30 seconds. As I say I am undecided if this is valid as I know now but it too a bit to work out.
Next task is to get that
PR through the roof which should be a doddle with this type of site....
Main thing is good quality links which bearing in mind your a resource site should be easy. Maybe you could work a system to entice the companies listed in your directory to add a banner or text link to your link pages which will be a link directory in-itself. This way you get your inbound link but don't make it a stipulation that you must link to you to get listed which isn't good.
2nd is making google like you better. You might consider using the title="xx" on your link menu. Not a fantastic earner but google does add weight to it and a great way of increasing your relavance and the odd nice keyword.
Other than that I am out of ideas.. Great site and good luck