There are some tools that i find myself using all the time on many of my projects. If they help me out they can probably help you out as well : ) I'll update this post as i come across other tools.
- Dataloader.io This web based data loader is a life saver. Its web based, you can match on actual names rather than ID's (Not recommended but i like having the option), and works on ALL editions!
- The Permissioner The Permissioner dramatically reduces the time involved with assigning and revoking permission sets assignments to multiple users. Using a simple interface, administrators can select one or more permission sets to assign to one or more users at a time.
- Rollup Helper Rollup Helper aggregates any Salesforce data in minutes. No coding required. Save time & money & unlock your data! Supports SUM, MAX/MIN, Formula-based Count, and Text Rollups. Rollup information using lookup relationships and through hierarchies.
- Perm Comparator A drag-and-drop tool for comparing profiles, permission sets, and users.
- Easy Describe EasyDescribe is a free Force.com developer tool to view and extract object metadata details. Don't waste time clicking through multiple screens to lookup recordtypes, field types, picklists, and other metadata. EasyDescribe it and get everything at once!
- Generate Test Data This site generates fake data in CSV format to use in sandbox testing!