Really, Web 2.0 is more a lifestyle choice than a specific technology !
Think of Web 2.0 as the evolution of web 'services' which add value to a user's online experience. An example might be the revolutionary Wikipedia community, where users interact and inform each other, compared to the static one-way publication of Encyclopedia Brittanica.
Online services like Google's GMail are also a good example of Web 2.0 principles at work. Powerful, searchable, flexible, accessible from anywhere. Focussed on user value, evolutionary value-add, tapping into the power of multiple databases and sources of specialised current information. They offer contextual and personalised add-ins such as advertisements only for products which match the user's profile and preferences. Compare that to the free email services of old, and you can see how different the original web is to the emerging "Web 2.0".
Where original web applications were written standalone and sold on their individual merits, Web 2.0 focusses on integration of many applications into a powerful suite of customer-focussed services, which combine to improve user's efficient access to information.
A key benefit of the Web 2.0 approach is the ability to standardise interfaces between many systems, meaning actual tools might be written in any language. Rather than leave the challenge of integrating myriad applications to the end user, Web 2.0 aims to provide seamless integration. This platform- and technology-independence means B2B (business to business) and B2C (business to consumer) interactions can flow much more smoothly, while drawing on various data sources to enhance the user experience.
Web 2.0 in the travel industry
The possibilities for Web 2.0 in online travel are limitless. From enhancing product distribution, syndicating content across multiple shopfronts, offering vertical and horizontal integration in your product offerings, Web 2.0 as a general concept makes the utmost sense in online travel.