Louie Helm has announced a two-month drive at Seventeen or Bust in an attempt to find another prime (or two or three) to help solve the Sierpinski problem:
http://www.seventeenorbust.com/
This project found their last prime just over six years ago at 3.9 million digits. Their status page shows that some candidates have been now searched up to 7.8 million digits. They certainly seem overdue for a prime.

For newcomers, this project uses the Prime95 software, but connecting to a different server. An alternative platform is also set up as a BOINC project under Primegrid:
http://www.primegrid.com/