While it's quirky in its search functionality and sometimes slow, Starostin's Etymological databases (link) has Pokorny's IEW (Indogermanisches etymologisches Wörterbuch) digitized and searchable. I have the brick & mortar version, but I still sometimes use his site when away from the home library. Watkin's root dictionary (part of the AHD4) always give the page number of the IEW for corss-reference purposes. (It's also availabe as a small booklet separate from the dictionary. The IEW also covers PIE roots that have no English reflexes. Starostin also has other dictionaries online, like Vasmer's Slavic etymological dictionary.

Ceci n'est pas un seing.