Once you've got your scrapbooking software, you will want to acquire some digital scrapbook papers and other elements.  While there are plenty of online stores to purchase kits from, there are also lots of free kits available online.

Two Peas In a Bucket offers traditional and digital scrapbooking supplies.  They also offer a free kit each month.  Currently there are 59 free kits online for download.
http://www.twopeasinabucket.com/shop/list/?f=c_336&c=24 (59 free digital kits)

Shabby Princess offers digital kits in a "shabby" style.  There are lots of kits available for purchase but there are also 22 free kits online for download.
http://www.shabbyprincess.com/downloads.asp (22 free digital kits)

Each month RAKscraps offers a free kit.  You can download the free kit at http://www.rakscraps.com/.  You will need to sign up for a free account first.

You can also find free kits, templates and other digital elements by reviewing the daily posts at both:
http://ikeagoddess.blogspot.com/

and
http://digifree.blogspot.com/
Both of these sites monitor several other sites and announce freebies that they find.