I'm a big proponent of Sybex materials.
They provide a clean presentation which is consistent across several certification programs.
For some, the material may be dry as compared to Mike Myers or the "For Dummies" series,
but others tend to like their study material without the filter.
Presented below are some of the Sybex study materials for five of the best known certification programs.
The CompTIA A+ certification is an entry level
certification which many companies look for when hiring computer support people.
It requires passing two exams.