Yahoo! Finance allows you to list all ETFs and sort by inception date or size.
Considering your follow-up question, though, I think you are asking the wrong question here. ETFs are a relatively recent innovation. Only 32 of these ETFs were around in 2000. For example, the Russell 2000 ETF (IWM), today's third most actively traded ETF overall, was only introduced in May 2000, thus missing your cutoff date. The CBOE only started listing options on SPY in 2006, and now it is one of the most liquid and popular options series. If your real goal is to backtest an ETF strategy, then think first about what indices/asset classes belong in your backtest then see what ETFs match those choices best.
Alternatively, start with what is most actively traded today. Unlike single stocks, a backtest involving index ETFs is not subject to backfill bias (a.k.a. survivorship bias) in quite the same way. Instead, you'll have to think hard about whether the index on which the ETF is based could reasonably have been considered one of a handful of popular indices as of your backtest date. Russell 2000 (EF: IWM) and MSCI EAFE (ETF: EFA) can reasonably be considered survivor-bias free index choices as of at least 1990, but Brazil (ETF: EWZ) wasn't on most people's radar until some time in the 2000s. This is despite the fact that their ETFs were all created around the same time.