Flash vs tripod?

I'm looking to make a purchase of either a Nikon flash or a tripod within a budget of roughly $200. I have a flimsy $10 tripod that is flimsy and will not survive my upcoming vacation to Europe. I primarily do city/walk-about photography, though I am also looking to get into sports photography and to do more portraiture in the near future as well. I often am frustrated while shooting (casually) indoors in low light around friends with the low-light performance of my camera and in not wanting to use the onboard flash. I am using a Nikon D40, and while the news of the day is focused on updated DSLR bodies, I am sticking to my budget and trying to improve my craft before I move up to a more advanced body (fingers still crossed that a D300s successor will be announced!). I should also add that I'm not particularly interested in the strobist stuff, but I am particularly interested in adding and learning bounce/fill flash to my skills.

I've found a few tripods on Amazon and local camera shops (Vanguard and Dolica brands) that are in the $100-$150 range that I am considering; I have been considering some used SB-600 and SB-700 flash units listed on Craigslist and the Fred Miranda buy-sell forum that are closer to $200+.

I'm open to any suggestions about my next move- a tripod for landscapes, long exposures, and potential sports shooting OR a flash unit for indoor event/people shooting?