I know there are some books dedicated to this. I just moved into a new apartment so paying for tutoring is not an option. Are there any useful resources to brush up on my business Japanese? Likely on the side but would still want to put in some amount of effort.

Here's the four best threads, newest to oldest, although I think its just chamcham recommending basically the same books every single time:

http://forum.koohii.com/showthread.php?tid=12053
http://forum.koohii.com/showthread.php?tid=10256
http://forum.koohii.com/showthread.php?tid=8120
http://forum.koohii.com/showthread.php?tid=5078

Also ALC has a whole series aimed at language leaners if you are looking for something slightly easier to get through:

http://www.amazon.co.jp/しごとの日本語-ビジネスマナー編...4757414676
http://www.amazon.co.jp/しごとの日本語―電話応対-基礎編...4757413319
http://www.amazon.co.jp/しごとの日本語-IT業務編-村上...4757414773
http://www.amazon.co.jp/しごとの日本語-メールの書き方編...4757413688