PageRank really doesn't matter. How many more times do I have to say that? It is just one of over 200 factors that Google considers when ranking a page, and it hasn't been a significant one for at least 5 years. Google realised that it made a big mistake by going so public with PageRank, and it just opened the system up to gamers, rendering it a thoroughly useless metric because it was too easy to manipulate.
The benefits you will get, in terms of direct traffic and reputation/relevance in search engines' eyes, of building useful links to and from suitable sites, far outweighs the minuscule downside of linking with low-PR pages. And to be honest, even then I'm not convinced that there is any potential damage. If it's a case of having a link from a low-PR page or not having a link from a low-PR page, Google isn't going to mark you down for having that link (if it did then it would be trivially easy to sink your competitors!), so you aren't going to lose by it.
But if you want to ignore Ted's advice and mine, you need to look at the actual page where the link is, not the homepage of the site. That's where a lot of people go wrong – they find a directory site with a home page of say PR6, and think that's a wonderful place to get links from. What they don't realise is that their link is at best on a page with PR1 and often not even that, and it's spread over hundreds if not thousands of outbound links on the page, so they're getting pretty much nothing at all from the link.