CapFriendly makes it relatively easy to look up all NHL-level signings:
Jarmo Kekalainen - CapFriendly - NHL Salary Caps
Hjalmarsson was a Blues draft pick; I don't know if he was ever associated with the Jackets. And I could've sworn there were at least two more -
indeed, there's at least one defenseman that I'm going absolutely mad trying to remember the guy's name but I can't find it anywhere; it was really early in his tenure. (Also, I'm not really counting Matiss Kivleneieks and Oleg Yevenko, as they were both already in North America at the time.)
EDIT: Found him!
Ilari Melart Hockey Stats and Profile at hockeydb.com
EDIT 2: In confirming Melart's contract info, I also was able to verify that Hjalmarsson was indeed here. I chalk up my remembering Melart but not Hjalmarsson to my well-established pro-defenseman bias.