Managing Fields Tips
How exactly is it going out of hand? Unless you have some kind of maximum number of tables you're allowed to have, 100 tables aren't really a problem. It's like this because this is the only way support multiple values per field.

The field storage system is pluggable, you can for example also use MongoDB to store your fields. The advantage of that is that it can store a complete content type in a single "document" and retrieve it with a single lookup/fetch. The downside is, you have to manage/maintain a second database server (and be able to so, which you aren't on shared webhosting for example).

See also The truth about field storage in Drupal 7. As linked from there, there is also a Per bundle storage project, but development stopped. Looks like nobody cares enough about this to maintain that module.