The No Prep Alternative--Print the page with the scrambled sentences, use sentences from your class's grammar book, or make up your own. Write the words for one sentence on the board in mixed-up order. I usually use a single column format, with all the nouns together, pronouns together, etc. Students work individually to arrange the words into a grammatically correct sentence. When they think they've got it, they cal you over to check. You can set a time limit to provide a little more structure. When the time is up, they can compare their answers with a partner or you can ask one or two students to write their sentences on the board.
Scrambled Sentences in Envelopes--This is my personal favorite. (I'm not sure where the idea came from, but I didn't make it up.) It's a fast paced fun game that really gets students thinking about grammatical form and syntax. It requires some preparation on your part, but if you keep the envelopes you can recycle them over and over again.
Preparation: Cut each sentence into words or groups of words. Put one the cards for one or two complete sentences into one envelope. You want a total of six or seven envelopes, all with different sentences. Each envelope should be numbered.
In-class: Divide the class into three or four teams. Have each team choose a team name. Write these names on the board. Under each name, write the numbers of the envelopes. Here's where the fun begins. Begin by giving each team one envelope. When they think they've got the right answer, they call you over to check. If it's correct, circle the number of that envelope on the board (under their team name) and give them a new envelope. The first team to correctly arrange the words in all the envelopes wins. Award a small prize to the winning team.