Yet another popular tool would be fxintel, but I hate using it since their site is chuck full of ads and slow.
Word of warning, be careful when comparing spreads. A lot of brokers play the spread game where they shift the cost of trading from the spread to commissions. Commissions are fine on their own, but some will charge a higher commission then offer lower spreads, meaning their total cost is about the same but they "appear" cheaper on these spread monitoring tools and sites.
Always do the math and find out the total cost of trading. When comparing brokers.