Use WOW3050DESK for 50% off on that 3050.
There's all sorts of coupon codes on the Dell site:
Dell Laptop Deals:
50% off Dell Precision 7520 Laptops (excl. Clearance and previous sales), plus free ground ship- use coupon code: LAPTOP7520
50% off Dell Latitude 7490 Laptops (excl. Clearance and previous sales), plus free ground ship - use coupon code: WEEKEND7490
$50 off Dell Latitude 7290 Laptops (excl. Clearance and previous sales), plus free ground ship – use coupon code: 4UONLY7290
50% off Dell Latitude 5400 Laptops (excl. Clearance and previous sales), plus free ground ship - use coupon code: LAPTOP5400
Dell Desktop Deals:
50% off Dell OptiPlex 5060 Desktops (excl. Clearance and previous sales), plus free ground ship- use coupon code: 4UONLY5060
40% off Dell OptiPlex 5070 Desktops (excl. Clearance and previous sales), plus free ground ship - use coupon code: YES2DELL5070
50% off Dell Precision 5820 Desktops (excl. Clearance and previous sales), plus free ground ship - use coupon code: WOW5820DESK
35% off Dell OptiPlex 7060 Desktops ( excl. Clearance and previous sales), plus free ground ship – use coupon code: DELL7060DESK
Super Saver: 50% off Dell OptiPlex 3050 Desktops ( excl.Clearance), plus free ground ship. Use coupon code: WOW3050DESK
This great deal is back!: 50% off Dell OptiPlex 7050 Desktops (excl. Clearance), plus free ground ship. Use coupon code: 4UONLY7050
For A Limited Time: 50% off Dell Precision 7520 Laptops ( excl. Clearance), free ground ship. Use coupon code: LAPTOP7520
For A Limited Time: 50% off Dell Precision 5820 Desktops (excl.Clearance), free ground ship. Use coupon code: WOW5820DESK
For A Limited Time: 50% off Latitude 5500 Laptops ( excl. Clearance), plus free ground ship. Use coupon code: LATITUDE5500
For A Limited Time: 50% off Latitude 5490 Laptops ( excl. Clearance), plus free ground ship. Use coupon code: WEEKEND5490
Too bad these don't work on clearance stuff, but pretty solid even without that.