Here are a few useful Salesforce Admin tools that every salesforce administrator would like to have.

Excel Connector: Used for manipulating data in salesforce.com from excel

This one is a really powerful tool especially if you love excel. You can extract data from salesforce directly into excel as well as make update from excel into Salesforce. There is an enterprise edition as well as a Professional edition. Based on your licensing download the appropriate edition. You do need office toolkit installed before using the Excel Connector

Excel Connector Installation: http://code.google.com/p/excel-connector/

Office Toolkit: Under Setup->Connect for Office after logging into salesforce or from http://code.google.com/p/excel-connector/downloads/detail?name=SForce_Office_Toolkit_MSI.zip&can=2&q=

Training Video on Using Excel Connector: https://salesforce.adobeconnect.com/_a13852757/p97003840

Salesforce.com DataLoader

This is window based application used for updating/manipulating data in salesforce.com. Can be used to update large amounts of data. Dataloader also has a interface that can be automate programmatically to schedule data load jobs. This can be downloaded from your salesforce environment. To download Apex Dataloader, login to your  salesforce environment go toData Management click on data loader from where you can download Apex Dataloader.
For steps how to download apex dataloader and insert records see this video :

Insert Records into to salesforce using Apex data loader

Force.com Explorer

This is a great tool test development of apex/SOQL queries as well as viewing the schema

You can install from http://wiki.developerforce.com/page/Apex_Explorer

Workbench

This is a great tool test development of apex/SOQL queries as well as viewing the schema which is browser based.

https://workbench.developerforce.com/

RoboForm

Are you are an administrator/developer who has access to multiple salesforce instances or access various websites which require you to login. The security policies of these website require you to frequently change the passwords. If you are wondering how would one remember the passwords for all these sites. The answer is a neat tool called RoboForm.

You can download and install RoboForm from www.roboform.com. Roboform creates a toolbar on the browser and asks everytime you enter the username and password if you want to save the username/password combination. Once you have it saved, next time you visit the site you can fill in the username and password just by a click of mouse button. Everytime you change the pwd it asks if it needs to update the password in roboform.

You can also create automatically generated strong passwords thereby having different strong passwords for different sites minimizing the risk of passwords getting into the hands of unwanted people. You would only require to remember only one password that of Roboform and roboform remembers the rest for you.

Chrome Plugins

Force.com LOGINS

This is very good utility to store your usernames,passwords and security tokens if you have many logins. Best of all its free. you can install this plugin from here