I recently picked up a Digitech RDS-8000 rack mounted delay. It has an eight second looped delay which I have found to work well for creating sonic washes and such. I don't think it would be enough for actual sections of songs.
The cool thing about the RDS-8000 that is different from other RDS series is the fact that for some reason Digitech decided to make all the controls knobs which is great if you like anolg interfaces. When I first got it I had a harder time stacking loops because I had to use a push button on the face of the rack, so I built a foot pedal to operate both the sample and bypass switches. The pedal helps for stacking on the fly. The RDS-8000 also has a mix knob for balancing the delay signal and the "straight " signal.
When I bought it it didn't have a manual so I haven't figured everything out yet, but for $60 it makes a pretty good entry level unit. The delay itself is classic Digitech, and the speed , feedback, and width knobs give alot of control. There are also two speed knobs: one for a gross settting which can not be changed while looping and another which can which allows you to slow down or spped up the sample (while also changing the pitch).
I hope this gives you all more insight into a great little "time machine". I would strongly recomend picking one up if you come across it. I f you have any questions feel free to contact me at email@example.com.