http://www.studyspanish.com: Grammar explanations, charts, and exercises. Some cost to subscribe, but there are still some good, free exercises available to use.
http://www.conjuguemos.com: A site where you can practice conjugating verbs; pick the verbs and tenses you want to practice from the lists provided. You will be timed; afterwards you'll learn how many verbs you got correctly in the amount of time you chose.
http://www.verbix.com/languages/spanish.shtml: Verbix—Free verb conjugator (for other sections you may have to pay). Enter a verb and it will show you all conjugations of the verb; pay attention to whether you are looking at the indicative or subjunctive side (we don’t get into subjunctive until the end of SPAN-201). Added benefit for multilingual students: it translates verbs into a variety of languages.