If you ordered during the "free shipping" week, these usually take longer due to heavy traffic, plus they wait for the whole thing to be over before shipping anything, so that if people drop multiple orders their stuff gets combined instead of Mondo having to foot the bill for every package separately.
Though in general with them the key is patience. Sometimes the stuff is in stock and they don't have much else going on that day and your order goes out within hours. Sometimes it takes days. Maybe even a week, if it's a really busy week. Their customer service is top notch, so just give it a few days and everything will be fine.