Alt+S will save the record you are editing and Alt+7 will save and add another. You can look at the source or use this jQuery discovery method to log the results to the console
$("[accesskey]")
<input type="button" value=" SAVE " id="saveButton" accesskey="s" onclick="DoSaveAdd()">
<input type="button" value="Save & Add Another" id="saveAndNextMenuOption" accesskey="7" onclick="DoSaveAddAndAnother()">
<input type="button" value=" SAVE " id="saveButton" accesskey="s" onclick="DoSaveAdd()">
<input type="button" value="Save & Add Another" id="saveAndNextMenuOption" accesskey="7" onclick="DoSaveAddAndAnother()">