I believe that tongues began at Pentecost in Acts 2 as a public sign to the unbelieving world that indeed Christ had come by His Spirit to indwell and empower His church (1 Corinthians 14:22). It was not a sign for the purpose of evangelism since an outsider coming into a church where people were speaking in tongues would think God's people were crazy (1 Corinthians 14:23). It was a sign to show to the world at large that the church had been established and the Holy Spirit had come. (fulfills the Old Testament prophecy referenced in 1 Corinthians 14:21). Speaking in tongues in the early church was accompanied by other miraculous, apostolic signs such as healings, miracles, prophecies, and interpretation of tongues (1 Corinthians 12:28-31, 2 Corinthians 12:12). Not all had the gift to be able to speak in tongues (1 Corinthians 12:4-11), given that the gifting was individual.
I believe that by and large the time period for these gifts has ceased as their purpose has largely ceased. Yet I am not a complete believer that these things never happen. God is free to act how He will, and indeed He still does heal and work miracles. I just don't believe He bestows these gifts on individual believers any longer. I believe these charismatic gifts, as they are commonly called, were relegated to the early church or what we might call the apostolic age where the foundation of the church was laid (Ephesians 2:20). I do believe that in areas where the gospel is going for the first time that these gifts may be manifested as evidence to unbelievers of the reality of the church. Indeed, it is not uncommon to hear instances of unusual workings of God on the mission field. However, I don't believe that these types of experiences are the norm any longer. 1 Corinthians 13:8 describes that tongues and prophecies will cease. I think as a general rule we must accept that this has happened, particularly in terms of any revelatory aspect of the gifts, given that the Word of God is complete (Revelation 22:18-19).
Where there is a belief that the charismatic gifts are still operating where the gospel has already been preached, there is often a lot of misunderstanding and abuse. The greatest abuse is probably to tell someone that they are less spiritual if they haven't experienced a baptism of the Spirit manifested by an outburst of speaking in tongues. Baptism in the Spirit is something that happens at the point of salvation; it is not a subsequent experience which reveals the super-spiritual among us (1 Corinthians 12:13). Even if the charismatic gifts were still active, Paul makes a point of downplaying the importance of tongues in 1 Corinthians 14, saying that speaking in tongues neither edifies or is as valuable as teaching, preaching, and prophesying. He didn't condemn speaking in tongues or praying in tongues, but his point was that it is better to have the mind be fruitful and for the church to be edified. If one speaks in tongues, neither he nor those listening can understand and be built up in Christ. Thus, Paul exhorted the believers to have the tongues be interpreted, interpretation being the complementary gift to speaking in tongues. Only two or three were to speak at once with interpretations to follow (1 Corinthians 14:26-27). This is rarely done properly in churches.
Finally, I think it is important that we understand tongues to be actual languages. For example, at Pentecost those from other nations and backgrounds were able to understand the gospel because they heard it in their language (Acts 2:8). There is no evidence whatsoever that speaking in tongues is gibberish or babbling (1 Corinthians 14:10-13). In fact, these kinds of utterances are forbidden by Christ who tells us not to pray in vain repetition (Matthew 6:7).
The Good News