I went to Yo Sushi today on Clarendon Street for their 'Blue Mondays' special offer.
Yo Sushi is a sushi restaurant (of course) with a trolley system. Sushi plates of various colours circle around, and you just pluck the ones you want off the trolley-belt. Mmmm. Normally the price of different colour plates vary, with fancier ones costing more. On Blue Mondays, everything is treated as a blue plate costing €3 - one of the cheapest options. The offer is expected to run every Monday for several more weeks.
I like Yo Sushi, but even with this offer it's pretty pricey. Still, worth a look.