While I’m not sure that the certificate itself will carry much weight with employers, what is interesting is how studying for the certificate forces you to investigate areas you’ve not previously explored, rounding out your knowledge.
The only cost is the exam itself, which at the test centre closest to me would cost £78 per exam (US$150), and you need to sit two exams for each level of certification. Should be an easy task to persuade an employer to stump up such a small amount for getting more knowledgable employees.
There are some books around to help too. Rob read LPIC I Exam Cram 2 and wrote a review of the book on Slashdot, but (sadly) his (admittedly profusive) use of (too many) parentheses drew a few less then complimentary comments. I noticed Amazon also have an O’Reilly book published in August which I guess would be more to date too – LPI Linux Certification in a Nutshell, 2nd Edition.