Following on from James's idea, I've decided to look for Travel-related sites first, and have started looking at Blogorama, a Blog directory that's worth bookmarking.
Means of transport:
The first one isn't a weblog and doesn't allow comments to be posted on actual entries, but it does have a guestboook, and is a fabulous travel site: The Man in Seat 61 is a site all about travelling by train.
Anne and Stephen's Big Adventure has now finished, but the blog of what happened to these two world travellers is still online and has a comments feature.
North America by bike is also over, but still online. No comments feature, however.
One way of approaching travel blogs could be by country. If the students choose a country and try to discover something about it's culture, geography, etc, as part of a wider project, it might be a good idea for them to check out some blogs about that country to get a more personal feel. They can always start by searching Google by entering the country they have chosen and 'blog' to get a selection.
Here are some I've just found that could be used, that also have commenting facilities:
Rolling Rains Report : "Precipitating Dialogue on Travel, Disability, and Universal Design"
Well, this is just a selection of sites. To be continued...