Selenium IDE: How do I get today's date?

Not sure what format your date is in, but you could do something like this:

<tr> 
        <td>storeEval</td> 
        <td>var d=new Date(); d.getDate()+'-'+((d.getMonth()+1)) 
+'-'+d.getFullYear();</td> 
        <td>date2</td> 
</tr> 
<tr> 
        <td>echo</td> 
        <td>${date2}</td> 
        <td></td> 
</tr> 

The line <td>var d=new Date(); d.getDate()+'-'+((d.getMonth()+1))+'-'+d.getFullYear();</td> works but returns the month as single-digit.

For my test case, I need the date returned in the format YYYY-MM-DD, so I use

<td>var d= new Date(); var m=((d.getMonth()+1)<10)?'0'+(d.getMonth()+1):(d.getMonth()+1); d.getFullYear()+"-"+m+"-"+d.getDate();</td>