Depends what you are after
If its cheap beer and lappies then look to eastern europe. Bratislava would do the trick. Prague and Budapest are great places but a bit more costly although you can do them for cheap if you dont get sucked in the tourist traps
Bit of sun, beer and the possibility of an STD then you need to look to Tenerife, Benidorm, Magaluf etc.
You might want to get a game of a majot team in so Madrid, Barca, Munich are all accessible enough.
My mate has just come back from Montenegro - never been but the new "in" place by all accouints