We are attending a conference in Bonn and flying home a week later from Frankfurt. Toying with getting to Prague or perhaps Italy- Rome maybe? but we don't want to spend all our time in transit ( thinking trains). Suggestions? We've been in France and Holland on other trips...want to try something new.

You're in Germany. See Germany, of course.

"we don't want to spend all our time in transit ( thinking trains)."

Near Bonn: 800+-year-old castles just to the south in Germany's Unesco World Heritage-preserved Rhine Valley:

www.marksburg.de
www.burg-eltz.de
www.st-goar.de/17-1-.html
http://www.falknerei-reichsburg-cochem.de/fotobuch.htm (falconry show at Cochem's Reichsburg Castle)

Lots of wineries and handsome fairy-tale villages there too - Cochem, Linz and Bacharach are among them:

http://www.cochem.de
http://www.linz.de/pdf/Linz_Prospekt_2007.pdf
http://www.bacharach-germany.net/

Trier - Germany's oldest city, with Roman history and ruins:

www.trier.de

A daypass called the Rheinland-Pfalz ticket will get you wherever you want to go within the mapped area on this page from Bonn south - 25€/2/day:

http://www.vrminfo.de/en/tickets-and...-pfalz-ticket/

Of course, the larger cities of Cologne, Aachen, Mainz and Frankfurt are also nearby.

With a week to use and the need to end up in Frankfurt, you have pretty much all of Germany at your feet. It would seem that you aren't really interested in staying there though.

Considering Italy, by train, with only 7 days to get there and back seems like a stretch. Unless you take night trains, you will spend the better part of 2 days in transport. Even Prague is stretching things given your desire not spend too much time traveling;

Bonn - Florence 11:00 hours
Bonn - Venice 12:00 hours
Bonn - Prague 8:00 hours

It is maybe an hour or so less from Frankfurt to those three destinations.

Without flying to your other destination, Germany, Belgium and Luxembourg would seem to be the only places fitting your needs.

Is it worth us making recommendations that would let you discover several different areas of Germany, Belgium and Luxembourg (well, the whole country, I guess) while staying within about a 4-5 hour train ride from FRA or are you interested in something farther away?

I'd stick with Germany. It's a great destination with lots of smaller towns that are also well worth seeing.

Germany is really my favorite travel destination. It has wonderful medieval towns (Rothenburg), Dinklesbühl, Nordlingen), castles (Heidelberg,Cochem, Neuschwanstein, and my favorite, Burg Eltz), gorgeous scenery.

Bonn is not a great distance from my favorite World Heritage Site, Quedlinburg. Fabulous place! And one of my favorite nature sites, the Spreewald.

And I'm leaving out all the major cities. I really like the smaller places better.

I really could go on and on.