<apex:page controller="myController">
<apex:pageblock>
     <apex:pageblockButtons>
          <apex:commandButton value="Save" action="{!saveObjects}"/>
     <apex:pageblockButtons/>
     <apex:pageblocksection>
          <apex:inputfield value="{!myA__c.Name}"/>
          <!-- add any other fields you want for this object -->
     </apex:pageblocksection>

     <apex:pageblocksection>
          <apex:inputfield value="{!myB__C.Color__c}"/>
          <apex:inputfield value="{!myB__C.Location__c}"/>
     </apex:pageblocksection>

</apex:pageblock>
</apex:page>

public class myController{

     public ObjectA__c myA      {get;set;}
     public ObjectB__c myB      {get;set;}

     public myController(){
          myA = new ObjectA__c();
          myB = new ObjectB__c();
     }

     public void saveObjects(){
          insert myA;
          myB.ObjectA__c = myA.Id;
          insert myB;
     }

}

public with sharing class MyExtension
{
    ApexPages.StandardController sc;
    public ObjectB__c objB {get; set;}

    public MyExtension(ApexPages.StandardController sc)
    {
        this.sc = sc;
        objB = new ObjectB__c();
    }

    public ApexPages.PageReference SaveBoth()
    {
        insert objB;
        return sc.Save();
    }
}

<apex:page standardController="ObjectA__c" extensions="MyExtension">
    <!-- snip -->
    <apex:inputField value="{!ObjectA__c.Name}"/>
    <apex:inputField value="{!objB.Name}"/>
    <apex:commandButton action="{!SaveBoth}" value="Save"/>