W3C announced the Mobile Web Best Practices 1.0 as Proposed Recommendation:

location based services


Written for designers of Web sites and content management systems, these guidelines describe how to author Web content that works well on mobile devices. Thirty organizations participating in the Mobile Web Initiative achieved consensus and encourage adoption and implementation of these guidelines to improve user experience and to achieve the goal of "one Web." Read about the Mobile Web Initiative.
That's actually a very interesting document. It's definitely a must for anybody targeting Mobile Web, which is a very different from the Web we know and it's not only because of limitations:
Mobile users typically have different interests to users of fixed or desktop devices. They are likely to have more immediate and goal-directed intentions than desktop Web users. Their intentions are often to find out specific pieces of information that are relevant to their context. An example of such a goal-directed application might be the user requiring specific information about schedules for a journey they are currently undertaking.
Equally, mobile users are typically less interested in lengthy documents or in browsing. The ergonomics of the device are frequently unsuitable for reading lengthy documents, and users will often only access such information from mobile devices as a last resort, because more convenient access is not available.
Still there is dream about "One Web":
The recommendations in this document are intended to improve the experience of the Web on mobile devices. While the recommendations are not specifically addressed at the desktop browsing experience, it must be understood that they are made in the context of wishing to work towards "One Web".
As discussed in the Scope document [Scope], One Web means making, as far as is reasonable, the same information and services available to users irrespective of the device they are using. However, it does not mean that exactly the same information is available in exactly the same representation across all devices. The context of mobile use, device capability variations, bandwidth issues and mobile network capabilities all affect the representation. Furthermore, some services and information are more suitable for and targeted at particular user contexts (see 5.1.1 Thematic Consistency of Resource Identified by a URI).
Some services have a primarily mobile appeal (location based services, for example). Some have a primarily mobile appeal but have a complementary desktop aspect (for instance for complex configuration tasks). Still others have a primarily desktop appeal but a complementary mobile aspect (possibly for alerting). Finally there will remain some Web applications that have a primarily desktop appeal (lengthy reference material, rich images, for example).
It is likely that application designers and service providers will wish to provide the best possible experience in the context in which their service has the most appeal. However, while services may be most appropriately experienced in one context or another, it is considered best practice to provide as reasonable experience as is possible given device limitations and not to exclude access from any particular class of device, except where this is necessary because of device limitations.
From the perspective of this document this means that services should be available as some variant of HTML over HTTP.
What about "Web 2.0"? Well,
No support for client side scripting.
I recently got Motorola RAZR V3X - cool 3G phone (btw 3G really rocks) and all of a sudden I'm all about Mobile Web. This is fascinating technology with huge future. I've got lots of plans that gonna make me millions... if I only had some more spare time :(