tour/cruise from St. Petersburg to Moscow

It would have to be a tour, since there's no water link between the two cities.

I don't know of any off-hand, but Lonely Planet's Russian edition should list some reputable travel agencies that specialize in Russian travel, which is important because the visa issues can get rather opaquely complicated. I would recommend a company called "White Nights", but because their website doesn't appear to work anymore, I think they may have gone out of business.

The best way is to phone a travel agent as soon as you land in STPB and ask him to book your tour. He will know all the tour companies and the itineraries. Wont cost any extra for him to do it for you. Most of the agents will speak English.

Be sure to check for the need of a visa even though you are on RS tour. Getting one took two weeks and $80 when I got it in 2001.

"Be sure to check for the need of a visa even though you are on RS tour." This is the main reason to contact a Russian travel agency, because the rules are confusing and subject to frequent changes.

There is a recent posting on Fodors.com by someone who took a Viking river cruise from St. Petersburg to Moscow.

http://www.fodors.com/forums/threadselect.jsp?fid=2

You will have to scroll down to Russia trip report/Viking

Brad's suggestion to read Fordor's reports is good. Scan down to number 111 on the referenced webpage where you will find several reports on travel in Russia. Since I have been to STPB and Moscow I found them interesting.

When you arrive in STPB (orMoscow) phone a travel agent and ask him to book a tour for you. He will know the best one and can meet your requirements.

Remember that there are tourists prices in Russia and lower nationals prices; so negotiate for the tour cost.