Tim Berners-Lee has published a set of notes that he has written after talks with various people in the UK and US governments. They are pretty rough and high level, but interesting to see the direction he is taking after his appointment.
It is good to see a health dose of realism already coming through, I hope it continues:
There are two philosophies to putting data on the web. The top-down one is to make a corporate or national plan, by getting committees together of all the interested parties, and make a consistent set of terms (ontology) into which everything fits. This in fact takes so long it is often never finished, and anyway does not in fact get corporate or national consensus in the end. The other method experience recommends is to do it bottom up. A top-level mandate is extremely valuable, but grass-roots action is essential. Put the data up where it is: join it together later.
A wise and cautious step is to make a thorough inventory of all the data you have, and figure out which dataset is going to be most cost-effective to put up as linked data. However, the survey may take longer than just doing it.
For any government agencies out there looking to put data online, you should take a serious read of these notes as they have some good solid advice.