I have noticed that more and more places in the UK are getting the 3D treatment in Virtual Earth, but there doesn't seem to be a list of all of them (at least I couldn't find one). The UK models do not yet support the recent enhancements that some of the US cities have (such as Denver or Las Vegas) where vegetation is modelled as well as the buildings, but I expect that it is just a matter of time.
So anyway I have created a collection of places in the UK where I have spotted 3D models - bear in mind you need to switch to 3D view (doh) and that it takes a while for the models to fully load (keep your eye on the globe in the bottom left corner of the map - if it has not filled with colour then the map and models are not yet fully loaded in all their glory (my son : "that doesn't look very good dad it's just a load of colours - oh hang on, wow!"
The collection is here - I'll add to it as I spot any others, or if you see or know of any others, please let me know. Some examples below:
UPDATE: Found this collection of worldwide 3D cities: http://maps.live.com/?v=2&cid=320432CACC287CB4!101&encType=1#
Cardiff Millennium Stadium
Bristol Cathedral
Royal Pavilion in Brighton
Some tips for the 3D view
Enable "Continue Earth motion after dragging"
This is buried in the options > 3d settings dialog > preferences section, but really adds a nice effect when dragging the map - and if you zoom out to the entire globe, you can spin it round like a football!
Try the 3D tour
You can open any collection and tour it in 3D - just click the link above the collection:
Create your own 3D tours
You can control how your 3D tours are viewed by recording the best viewpoints, and adding info and images.
When you create a collection in 3D the properties for any pushpin has specific 3D options (shown below) such as capturing the current viewpoint, adding animations, waiting for the scene to load, and waiting before moving to the next pushpin.
In the collections editor you can then select Actions > Tour and make videos in 3D.
Turn your 3D tour into a video
It's really easy to turn a 3D tour into a video: In 3D tour window, just click the Record button, select some display options and click continue. It can take quite a while though, so you'll probably want to kick it off and go and make a cup of tea! Note that it does not seem to be too processor intensive for your machine, perhaps most of the work is being done on the server, so you could do some work rather than have a cup of tea, if you are that way inclined.
NOTE: The quality of the video can be set right up to HD quality, You need to do this before you click the record button in the options screen for VE (Click the options icon top right of the screen 
). However my laptop (Lenovo T61p with 4GB Ram and Vista x64) fell over with an out of memory error when I tried to create a video at the highest 1920x1080 setting.
Host the video with Silverlight Streaming
if you create a video it is really very easy to host it for free at http://silverlight.live.com and embed it on any page you want (using Microsoft's bandwidth and infrastructure). This is free at the moment, and will remain so when the service goes live, provided you are happy for ads to appear on your videos. If you don't want ads then there will be a paid for service, or you can host the video yourself. Here's one I created earlier of a tour of the River Thames: