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Nick_W is right but if you have too much pages to link to you can link to some sort of Sitemap that will have links to most important pages of your site.
Google have recently reactivated domain that was banned because of those 1 pixel gif trick so we know they catch it but i would bet it's because people have set the width=1 and the height=1 otherwise without those "hints" it would be hard for a spider to see a 12 X 50 pixels transparent gif image since you would need OCR to do that and i don't think Google or any other SEs are there yet.
In other words it's at your own risk my friend :-D
Mtlinfo
was a bit concerned that it might seem too devious.
If it's being done purely to manipulate PR or search results without any benefit to your users, then it most certainly will be judged as "devious".
While it may not be flagged by the spiders, if you achieve a high enough ranking in the SERPs, you can be assured that disgruntled competitors will go over your page with a fine tooth comb just looking for an excuse to report you to the SE's.
As a general rule of thumb, unless you are more than willing to sacrifice a site's long term viability for short term success, don't do anything that wouldn't pass muster under the scrutiny of a manual review from an SE editor.
If it's being done purely to manipulate PR or search results without any benefit to your users, then it most certainly will be judged as "devious".
Actually, if it's being done purely to manipulate PR or search results without any benefit to your users, then it is, by definition, devious.
In answer to your original question, you should probably just put text links in pages.