I got a lot of responses on my personal journal and in the two communities I posted to. Thanks to everyone for sharing, and for your encouragement. I've thought & prayed about all this for several days, and I'd like to share my conclusions.
But before I do that... My husband pulled up the Wikipedia on glossolalia, which is the technical term for speaking in tongues. Here's the link: http://en.wikipedia.org/wiki/Glossolalia
There were several interesting points in the wiki that I'd like to share, but I encourage you to go read the wiki for yourself. It gives a lot of scientific facts, and a lot of Church history. Very interesting. Here are some quotes and comments.
"Samarin found that the resemblance to human language was merely on the surface, and so concluded that glossolalia is "only a facade of language". He reached this conclusion because the syllable string did not form words, the stream of speech was not internally organised, and - most importantly of all - there was no systematic relationship between units of speech and concepts. Humans use language to communicate, but glossolalia does not."
"The material explanation arrived at by a number of studies is that glossolalia is "learned behavior". What is taught is the ability to produce language-like speech."
In the section on Church history, it becomes evident that from about 500 A.D. to 1901, it was almost unheard of for anyone to speak in tongues. Yet the work of the Holy Spirit in spreading the Church is evident.
"Glossolalia has also been observed in the Voodoo religion of Haiti, as well as in the Hindu Gurus and Fakirs of India."
So. My conclusions. First of all, there are two main purposes to speaking in tongues. The first is to bring a person emotionally closer to God in private prayer. The second is to edify the Church, if there is someone to interpret, as Paul said in 1 Corinthians 14:27-28.
As far as what speaking in tongues really is, I'm not sure. Since glossolalia happens in other religions, and it can be taught with little effort, and since linguists conclude that it is not a real language, I don't buy that it's a heavenly language.
However, there is the possibility that speaking in tongues is actually xenoglossy, speaking in an unlearned (human) language. Except that some people went as missionaries to foreign countries and tried speaking in tongues to communicate with the natives, who did not understand them at all. Not saying that xenoglossy doesn't happen, but the typical speaking in tongues you hear at a Pentacostal Church is glossolalia, not xenoglossy.
Thirdly, God has made it clear to me that I do have the Holy Spirit within me. I may not have some of the "flashy" gifts like speaking in tongues, healing and prophesy, but that doesn't mean the Spirit is absent.
1 Corinthians 12:8-11 says, "To one there is given through the Spirit the message of wisdom, to another the message of knowledge by means of the same Spirit, to another faith by the same Spirit, to another gifts of healing by that one Spirit, to another miraculous powers, to another prophecy, to another distinguishing between spirits, to another speaking in different kinds of tongues, and to still another the interpretation of tongues. All these are the work of one and the same Spirit, and he gives them to each one, just as he determines."
I have the distinguishing between spirits, also known as discernment. This passage makes it very clear that not everyone has the gift of speaking in tongues, and that the Spirit gives these gifts to each person as he determines. It's not my place to try to force the gift of tongues; if God wants me to have it, He'll give it to me.
Which also leads me to believe that gifts are given at the time of need. That need may be for the Christian's edification, or so that they can use the gift to lead others to Christ. In either case, there has not been a need in my life for the gift of tongues. And I'm o.k. with that.
Some of you may disagree with my conclusions, and if you want to share the reasons why you disagree, please do so with love. If you can't speak kindly to me, please remain silent. After all, brothers & sisters in Christ are to treat each other with the same love Christ gave us, right?
Again, thanks to everyone who commented, and especially thanks to those who prayed that God would lead me into the Truth.