There are a few tools I use more or less often when playing with Salesforce and this one is one of them. Few people know it but it would really deserve to be better known! It has been created before Salesforce introduce the Schema Builder. If the Schema Builder is not bad and probably easier to use, you are very limited with what you can draw, the export options, ...
With this tool, you generate a bunch of html files with the objects of your choice and you can click and navigate between the different objects, very powerful!
You can download it at this address
Follow this notice in order to install it and depending on the platform, you may need to escape characters differently (especially the "-cp" parameter). Instructions are a bit confusing in order to run the command line successfully for your first export, but this command should run definitely on Mac:
java -cp schemaSpy_5.0.0.jar:force-metadata-jdbc-driver-2.2.jar net.sourceforge.schemaspy.Main -t force -u SALESFORCE_USERNAME -p SALESFORCE_PASSWORD -font Arial -fontsize 8 -hq -norows -o doc -connprops "includes\=Account,Contact;url\=https://test.salesforce.com/services/Soap/u/23.0" -norows -charset utf8 -db force -desc "ExtractDir"
https://login.salesforce.com if you are in a live Org.