YN460-II if you're not bothered about TTL, they're 40 quid each.
SB-600 is the cheapest Nikon flash that has TTL support for your D5000.
if i can get 2 for 100 bonus lol (i should get myself on dickinsons real deal)
If going with off-brand flashes, you also have to consider how you're going to trigger them if you go for more than one flash.
So, make sure you get ones with decent quality optical slave sensor in them, and you'll probably lose TTL anyway (most iTTL capable 3rd party flashes only support it on the hotshoe or a TTL cable, not wirelessly). Or, just use radio triggers.
Personally, I'd go with a couple of YN460-II flashes and RF-602 radio triggers.

very true. the Nissin seems to dislike wireless hotshoe triggers, but should work fine on a cable (with TTL). i do believe it works ok with built-in commanders, but i have no idea if the D5000 has that functionality or not.![]()
It doesn't, you'd need either an SB800/900 or an SU800 on the hitshoe to get wireless CLS
I'm interested! I've been searching for older Nikon speedlights for ages.I have a nikon sb 26 that I may want to sell