I have both the sb600 and the sb800 and both are excellent IMO. Might be worth looking for a second hand one of these if cash is a concern.
If you're not totally tied to Nikon, then you may want to consider either the nissin or yongnuo ranges of flashes. Personally, I do not rate the nissins, but the yongnuo are rather good IMO and feel solidly built.
I picked up a brand new manual only flash for about £50 (for strobist stuff) and IIRC their entry level TTL compatible flash is only £60 - they do of course make higher spec'd models.