I hope you're seeing groups more quickly and reliably now. If you're still missing atari's (when a stone or group can be captured on the next move) don't worry, just keep playing.
On this leg of the journey I want you to pay special attention to attachments. An attachment -- or contact play -- is a stone not connected to friendly stones, played on a liberty (an adjacent empty intersection) of an enemy stone which may be a single stone or part of a group. The large majority of attachments are played against single stones.
Attachments are extremely important in go because the player who plays next can get much better local development. This is easy to see in these diagrams (also in the attached file). When black moves next (right) the sequence gives black a dominant position over two thirds of the board. But when white plays next (left), white gets the dominant position. The factor that drives this result is shortage of liberties. After Black 5, for example, white must make a protective move to prevent black from forcing a capture with his next move.
Although you should not expect a real game to develop the same way as these diagrams, the logic driving the sequences is exactly the same as in real game play. The superior position the first to play after an attachment gets illustrates the same advantage possible in a real game.
By the way, if the responding player does not like the result of a sequence like that shown in the example diagrams, the correct answer is not to hane like 3, but instead to extend to 7 or 10.
I hope the importance of play after contact moves is now clearer to you. Pay special attention to contact plays. Don't go out of your way to play them, but don't be afraid of them. Press the opponent if it seems right, and play calmly if it seems right. But be very careful to watch your liberties because it's easy to lose stones when black and white get entangled.
Working with attachments help continue to learn to see fundamental patterns in go. In addition, on this leg of the journey, you will start developing the skills that will become what we call reading, which is the ability to see multi-move sequences. You should probably still play on small boards for now, although there is nothing wrong with playing on the full board at this time.