It really depends on what specific topic you're interested in. There are specific websites, distribution lists and blogs for many topics and nice sub-topics. There's even paid reports on 'insider' information. We'd suggest our blog for hotel tutorials (www.hoteliyo.com/tutorials). Also, check out Skift.com. If you'd like to know more, we can offer a short call to assist.

Marriott's "spirit to serve"
Ritz Carlton's book - Gold Standard
Ron Kaufman's books on Service
Jack welch's winning
Successful managers handbook (great for your junior managers)
24 Selling Techniques by Brain Tracy