Starbucks lets you place an order using Alexa with the Starbucks Reorder skill. After you enable the skill, you will need to link your account. The skill will not work unless you've previously placed a mobile order with the Starbucks app on Android or iOS. It can place an order at one of the last 10 Starbucks locations you've visited in person. You can also check your account balance and switch between your five previous mobile orders.
Alexa Skills themselves are quite helpful. However, even with an updated Skills section in the Alexa app and the ability to add skills using only your voice, discovering new and useful skills is a less than desirable experience. So much so that Amazon actually created a skill called Skill Finder which, you guessed it, helps you discover new skills. Launch it by saying, "Alexa, open Skill Finder" or "Alexa, tell Skill Finder to give me the skill of the day."
In the Alexa app, this is achieved by selecting the main menu button (found in the upper left-hand corner of the screen) and choosing the Skills option. From here you can browse Alexa skills by category or other criteria such as those favored the most by its large user base. You can also search for skills by keyword or name through this same interface.
If you want to do some casual research for a future trip, you can get fare estimates using the Kayak skill. You can say, "Alexa, ask Kayak where I can go for $400" or "Alexa, ask Kayak how much it costs to fly from Los Angeles to Dublin." The skill will ask for additional information and eventually provide you with a series of options and price ranges.