To do Thunderbolt daisy chaining to a non-Thunderbolt monitor, you need another device between the Thunderbolt display and the monitor.
For example a Thunderbolt hard drive that supports daisy chaining.
Then you would have this setup:
Macbook -> Thunderbolt Display -> Thunderbolt hard drive -> Mini-Displayport to (Displayport, DVI, HDMI, VGA)
Another possible configuration would be two of the Dell monitors and a Matrox Dual Head 2 Go adapter, which combines two monitors of the same resolution into a single monitor as far as the computer is concerned.
As someone else said above you could also get a USB video adapter. This would basically act as its own low-power video card, rather than using the system's video card for that display. They generally work fine for basic tasks but may not be great for things like high res video playback or games.