I went to the Fidelity website this morning and noticed that starting today they are offering free trading on 25 iShares ETFs. This is a great news for the people who don't have a large sum of money to invest because they can get diversification by buying different ETFs commission-free. ETFs have a couple big advantages over mutual funds:
1. No minimum amount to invest. You can buy a single share of an ETF and pay $0 commission.
2. You can sell ETF any time with no commission, unlike no transaction fee mutual funds where you often have to pay a fee if you sell within a certain period.
In addition Fidelity lowered their commission to $7.95 on all other trades, which is a pretty good price.
More Info Here