Not as popular as it once was.
One of the most popular has been the MCSE.
It is always good to have some network knowledge.
One of the most challenging exams in the industry. All hands-on lab
Not very difficult, but shows some knowledge of hardware, and is a
prerequsite for HP exams
HP Acredited Platform Specialist. Requires CNE, or MCSE and A+ as
prerequsites, but is a fairly easy exam that deals mainly with hardware.
Oracle, Citrix, etc.
There is plenty of demand for MCSE's, but experience counts as well.
RHCE is another important one, as is the CCNA. Other certs are useful,
but more so in smaller companies, or as a consultant. You will need
more experience to get into a big company, but jobs tend to be more
specialized. You would either be a server admin, network admin, or dba,
whereas in a smaller company you might be all three.
Another important thing to help get interviews is a college degree. You
can use some of your certifications for college credit.