Can anyone suggest a way for me to split an approximate 500MB rar file into chunks about 12MB large, that I can give to a Windows User and have them rejoin the files? Optimally I would like to do Rar splitting but I cannot find any Linux utility to handle this.

This one works well on both windows on Linux - although you may need to use the java version intead of the HJsplit for Linux. It's the same thing but the java version doesn't produce any dependency issues (as long as you've got at least a jre).

http://www.freebyte.com/hjsplit/

Just download the LXSPLIT software from ( http://www.freebyte.com/download/lxsplit.tar.gz ).
untar it using the command

$ tar -xvzf lxsplit.tar.gz
$ cd lxsplit-0.1.1/
Here just follow the instruction given in the README file. It's very easy to install.
After installing you can split the files using the command line

$ lxsplit -s filename size
for example if you want to split a 700 mb file named "something.avi" into 7 pieces each of 100 mb then just type
$ lxsplit -s something.avi 100m

Here "-s" stand for splitting
"100m" stands for size of the splitted file.

after this you can see the splitted file in the same directory named

something.avi.001
something.avi.002
something.avi.003
something.avi.004
something.avi.005
something.avi.006
something.avi.007


For joining the splitted file just type
$ lxsplit -j filename.001

Here "-j" stands for joining and remember you have to type the name of the first splitted file i.e. " filename.001".It automatically searches for the rest of the file in the same directory.