This is by no means an exhaustive list. But all these breweries run visits on a regular basis (as far as I can find out today). Some of the larger breweries that used to do so, like Caledonian in Edinburg, have now stopped - a pity, since Caley's (as it's affectionately known) is a real museum of brewing history. And I know I have missed a good few out. But if you're that interested in beer you'll know where to find them!
* Elgood's Brewery, Wisbech, UK. Out in the wilds, but it's a good family run brewery and has rather good gardens for those of you who might not be quite so much into beer.
*A double brewery trip if you can get to Masham, Yorkshire. Theakstons Brewery, and its rival Black Sheep - started by a Theakston who left the family business when it was sold to a big brewer (it's now back in family hands).
*Batemans in Lincolnshire can be highly recommended. You get a windmill as well as a brewery and the beer is superb. But you may be beginning to get a bit of a theme here - the best brewery tours in England all seem to be a bit out of the way. Nothing nice and central in London, for instance. Most city centre breweries and maltings are now conference centres and hotels. But there's one notable exception:
* Hydes, in Manchester. And they still brew an excellent mild - not a style that's particularly fashionable today, but with its light hopping and sweet malty notes, one I happen to like a lot.
* Many of the Munich breweries only put on tours for groups. However, Erdinger, which makes one of the best wheat beers in the world, just asks you to phone for a booking. And Andechs, a little way out of Munich, also has an interesting tour - though only in German; but there's the opportunity to enjoy the beer and good solid food in the brewery pub (Braustuberl).
* Plzensky Prazdroj, better known to most as Pilsner Urquell, operates tours. If you've got time to go out of your way, so does its smaller sister Velke Popovice - though the tours are only in Czech. And if you really want to get lost in the back of beyond, an expert beerhunter has uploaded his account of a visit to a microbrewery in a castle in south Moravia, on the way to Brno.
* Staropramen has a new visitors' centre, opened in 2005, in the Smichov district of Prague. If you're short on time this is probably the easiest beer visit in the Czech Republic. To see Budweiser/Budvar, you have to go out to Ceske Budovice (yes, that's how it got its name) - and most of the tours are for parties, but the tour after lunch is for everybody, no reservations.
* The New York Times did my job for me on Belgium!
* In France, Strasbourg is the home of Kronenbourg, giant of French brewing. At the other end of the scale, Brasserie Hotteterre, in Normandy, brews what I think is better beer than Kronenbourg in its village farmhouse headquarters, about an hour's drive from Rouen (closer to Evreux).
I'll hope to add a few more as I go - and any comments would also be welcome. But that should be enough to keep beer lovers happy for a while!