The traditional distinction goes like this: the singular regard is correct in phrases like with regard to and in regard to where these phrases mean with reference to, while the plural regards means good wishes expressing respect, affection, or condolences. But while some people continue to insist that using regards in place of regard is simply incorrect, the old distinction is not consistently borne out in real-world, 21st-century usage. Regards is commonly used both ways, both in edited writing and elsewhere.
With regards to, etc.
With regards to sushi offerings in Evanston, there are still many other fish in the sea. [Daily Northwestern]
Reality television holds a unique position in the television landscape in regards to racial discourse. [AV Club]
In 2009, he was charged with assault and criminal mischief in regards to his then wife. [Guardian]
With regard to, etc.
Times, then, have changed with regard to ideas of decorum for these ancient buildings and their custodians. [Telegraph]
The platform makes no mention of changing bankruptcy laws in regard to pensions or disability payments. [Ottawa Citizen]
Regards (traditional sense)
Kurtz urged him to convalesce, and passed along his regards to those attending the dinner. [Coldwater Daily Reporter]
The Watchdog and his pals send a chorus of woofs to the Kansas City traffic guys for giving their regards to Broadway. [Kansas City Star]