Even though it's a bit beyond where I am right now with Linux, I was impressed with Susan Douglas and Korry Douglas's book Linux Timesaving Techniques For Dummies (Wiley). There are a lot of gems found in these pages...
Chapter List: Making The Desktop Work for You; Getting the Most from Your File System; Good Housekeeping with Linux; Tweaking the Kernal on Your Linux System; Securing Your Workspace; Networking Like a Professional; Monitoring Your System; Serving Up the Internet and More; Backing Up Means Never Having to Say You're Sorry; Programming Tricks; The Scary (Or Fun!) Stuff; Index
In many ways, this reminds me of a Hacks-style book. There are 62 techniques outlined here that you can use to make sure your system is running at peak efficiency or to save you time during normal administration chores. It's targeted for Fedora Core 2, SuSe, and Mandrake, so if you're running one of those distributions, you should be able to benefit from the information. So what are some of the techniques? #44 helps you get a MySQL server up and running quickly. #24 helps you learn how to customize your Linux kernel if you're really into that sort of thing. #22, Spring Cleaning Essentials, is also very beneficial both from an efficiency standpoint (fewer active processes) and a security standpoint (fewer potential paths into your system). All the tips are like this... very practical, and well documented.
And if you've had the impression that Dummies titles are majorly dumbed down, this volume will squelch that opinion. There's nothing in this book that pertains to "dummies". I consider this a good read for someone who has a few months of active Linux experience under their belt, and they want to start exploring a few topics that start to wander from just the basic commands. I'll be keeping this one with the rest of my Linux titles, and hopefully about six months from now I'll realize the full benefit from it.