Author: Christoph Knabe

I looked for a tool with the following features:

capable of drawing UML diagrams
export them in a vector graphics format (EPS, WMF, SVG, ...)
easy to import those diagrams into a word processor (OpenOffice or Word)
which should be free for educational purposes

Also other people had difficulties in finding that. My results here are:

Tool Export Formats Free? Notes

UMLet 7 EPS, SVG, PDF for all Simple Java UML drawing tool. Export EPS, insert into Word/OpenOffice works OK. Very active developer.
Dia 0.88 CGM, EPS, HPGL, SVG, WMF for all Multi-paradigm drawing tool. Export EPS, insert into OpenOffice works OK, but umlauts in text are exported as UTF-8 and have to be post-edited to Latin-1.
Argo/UML 0.15.1 PS, EPS, SVG for all UML tool. Export PS, convert by GhostScript to EPS, insert into OpenOffice works OK with umlauts and bounding..
Together 5.5 GIF, WMF, SVG for educational institutions UML tool. GIF works OK, but is bitmap. WMF works buggy (borders truncate texts as of font problems). SVG not tested.
Rational Rose C++ 4.0.14 MS-OLE-Object I think not UML tool. Single diagram: Select all, paste in Word, works well scalably
Poseidon for UML CE 1.0 GIF, PS, EPS, SVG for all UML tool. GIF works, but unexactly. EPS works buggy (texts overwrite borders as of font problems). SVG not tested.
DoME (Domain Modelling Environment) 5.3 GIF, PS, EPS, SVG for all Multi-paradigm drawing tool. GIF works, EPS fails. Sometimes unclear behaviour.
Generating Objects 1.0 none for all Simple UML drawing only tool, nice printout
Eclipse with plugin EclipseUML ? for all Powerful Java-IDE with many plugins. Not yet tested.
Umbrello EPS ? Supposedly epstowedit can convert eps to dxf or wmf which can be used in OO (Hint by Niels Elgaard Larsen).
Remarks:

Tool	Export Formats	Free?	Notes
UMLet 7	EPS, SVG, PDF	for all	Simple Java UML drawing tool. Export EPS, insert into Word/OpenOffice works OK. Very active developer.
Dia 0.88	CGM, EPS, HPGL, SVG, WMF	for all	Multi-paradigm drawing tool. Export EPS, insert into OpenOffice works OK, but umlauts in text are exported as UTF-8 and have to be post-edited to Latin-1.
Argo/UML 0.15.1	PS, EPS, SVG	for all	UML tool. Export PS, convert by GhostScript to EPS, insert into OpenOffice works OK with umlauts and bounding..
Together 5.5	GIF, WMF, SVG	for educational institutions	UML tool. GIF works OK, but is bitmap. WMF works buggy (borders truncate texts as of font problems). SVG not tested.
Rational Rose C++ 4.0.14	MS-OLE-Object	I think not	UML tool. Single diagram: Select all, paste in Word, works well scalably
Poseidon for UML CE 1.0	GIF, PS, EPS, SVG	for all	UML tool. GIF works, but unexactly. EPS works buggy (texts overwrite borders as of font problems). SVG not tested.
DoME (Domain Modelling Environment) 5.3	GIF, PS, EPS, SVG	for all	Multi-paradigm drawing tool. GIF works, EPS fails. Sometimes unclear behaviour.
Generating Objects 1.0	none	for all	Simple UML drawing only tool, nice printout
Eclipse with plugin EclipseUML	?	for all	Powerful Java-IDE with many plugins. Not yet tested.
Umbrello	EPS	?	Supposedly epstowedit can convert eps to dxf or wmf which can be used in OO (Hint by Niels Elgaard Larsen).

EPS graphics cannot be viewed in the word processor, but only after printing to a PostScript printer or to AcrobatDistiller or to a PDF printer driver. You should edit an EPS graphics by GhostView and add a preview bitmap graphics. Then you can see a low quality graphics in the word processor, but have high quality text rendering in the final PDF printing.
SVG is not accepted by OpenOffice.org 2.0, but I read about a plugin.

Please inform me, if you find a tool that fulfils such criteria!

A better list you can find at Michael W. Godfrey @ UWaterloo