When developing a simple form to use in your WordPress theme or plugin you often want to post to the same page.
To do so, simply leave the action attribute empty in your form.
<form action="" method="post"> <div> <label>Name</label><br /> <input type="text" name="your_name" /> <input type="submit" value="Send" /> </div> </form>
Notice that your_name is used, using simply name as the attribute value may cause some trouble. At least it did for me.
Mark Jaquith has written a bit more detailed about the action attribute.