I brought maybe a pound of hop plugs from America to Croatia earlier this year with no problem, in my checked bag. I have also ordered hops from Freshops, Steinbarts and Maryland homebrew to be delivered here and they all arrived with no trouble.
Also, there's a great online shop in Belgium for mail order. I order from them regularly. They have great hops, but only Cascade of the American ones, and those are expensive. But they have great Challenger, East Kent Goldings, Fuggles and some Hallertauer Hersbrucker for very cheap.
They're called Brouwland:
http://www.brouwland.com/en/
They also have lots of supplies that are useful: auto siphons, salts for brewing, iodophor, irish moss, litmus papers etc etc. I thank God that they're there. Makes my life easier.
Here's the links to the other places I've found in the States who will ship to Europe. Steinbarts are particularly friendly. I've placed a few smaller orders with them and they're willing to send it with the cheapest postage, which isn't so bad. It was $13 or something. Freshops and Maryland Homebrew were also willing to use this, so shipping for lighter things such as hops is not something you can't do.
Also, all of those orders took almost exactly two weeks to arrive from when they shipped. Belgium is probably quicker as I live out in the wilds of the Balkans.
;-)
With Brouwland, it always takes three weeks for me. But when I called them, they said it was because they ship stuff to my area all at once, so they're usually only doing it once or twice a month. If you're IN Belgium, it should be much faster. They're in Beverlo, so if you're near there, guess you could drive there.
http://www.fhsteinbart.com/about.html
Maryland Homebrew
http://www.freshops.com/#
And here's the postage calculator:
http://ircalc.usps.gov/default.aspx?Mode=Intl_Single&CID=10033
A "small flat rate box" using International Priority, that weighs one pound, going to Belgium, will cost you $13 in shipping. Not bad at all. I think when I ordered from Freshops it was twice that, ordering around 20 oz. But those whole hops are large.
Hope this helps.