This YouTube playlist walks you through many of the other Google Voice features.
On a related note, Wes Fryer recently wrote a post with detailed directions on how to send text messages from a Google Docs Spreadsheet.
Applications for Education
One of the reasons that I have put my Google Voice number on my syllabus this year is because I know that students are much more likely to text a question than they are to email me with a question (nevermind call, that's so 20th Century). The other reason is that I am hoping parents too will prefer the text option over the calling option because I am notoriously slow at checking the archaic voicemail system at my school (I think it still uses actual cassette tapes). If I'm at my computer I can provide almost instant responses to my students' questions.