It's hard enough to find the time to get behind the kit so when you do, make sure you spend your time wisely.
I'll be continually adding ideas to help you practice the best way, here's a few points to get you going.

Make the most of your time
First of all try and schedule practice time into your working week.
Set a practice routine and stick to it!
A little and often is often the best way to achieve consistency.
Make a list of areas of weakness' you wish to improve upon.
Keep a practice diary so you can see how you are progressing.
Practice with a metronome as much as possible.
Set goals for each practice session or have weekly/monthly aims.
Have a list of songs that you want to be able to play to and work these into your practice routine.
Play to music you wouldn't normally listen to for inspiration and to push you out of your comfort zone.

Other ideas
Always find time to record or video yourself playing.
Set up a mirror to check posture and technique
Keep a practice pad next to the sofa and practice while watching TV/in advert breaks!
Go to gigs, any gig. Even if it's a style of music you're not into.
Go to jam nights, playing with other musicians is such an important thing to do.
Study other drummers, either online or even better in person! Use your eyes as well as ears!

Books and other material that I recommend:
The New Breed by Gary Chester 
Stick Control by George Lawrence Stone 
The All-American Drummer by Charley Wilcoxon
Mind Over Meter by James Hester
The Encyclopedia Of Double Bass Drumming by Bobby Rondinelli
Rockschool Grade books
Go through the Rudiments. You can find these on the Vic Firth website.  

DVDs that I recommend
Beyond The Chops by Aaron Spears
Secret Weapons For The Modern Drummer I and II by Jojo Mayer
Back To Basics and The Next Step by Dave Weckl
Modern Drummer Festival DVDs