Here is a nice robots.txt file that will allow the good bots to enter and keep out the bad bots.
 
 
			#
 # robots.txt generated by www.1-hit.com's robot generator
 # Please, we do NOT allow nonauthorized robots any longer.
 #
 User-agent: *
 Disallow: /cgi-bin/
 
 User-agent: googlebot
 
 User-agent: Scooter
 
 User-agent: Openbot
 
 User-agent: fast
 
 User-agent: ZyBorg 
 
 User-agent: Slurp
 
 User-agent: Googlebot-Image
 
 User-agent: msnbot
 
 
 User-agent: URL_Spider_Pro
 Disallow: /
 
 User-agent: CherryPicker
 Disallow: /
 
 User-agent: EmailCollector
 Disallow: /
 
 User-agent: EmailSiphon
 Disallow: /
 
 User-agent: WebBandit
 Disallow: /
 
 User-agent: EmailWolf
 Disallow: /
 
 User-agent: ExtractorPro
 Disallow: /
 
 User-agent: CopyRightCheck
 Disallow: /
 
 User-agent: Crescent
 Disallow: /
 
 User-agent: SiteSnagger
 Disallow: /
 
 User-agent: ProWebWalker
 Disallow: /
 
 User-agent: CheeseBot
 Disallow: /
 
 User-agent: LNSpiderguy
 Disallow: /
 
 User-agent: Black Hole
 Disallow: /
 
 User-agent: Titan
 Disallow: /
 
 User-agent: WebStripper
 Disallow: /
 
 User-agent: NetMechanic
 Disallow: /
 
 User-agent: Wget
 Disallow: /
 
 User-agent: mozilla/4
 Disallow: /
 
 User-agent: mozilla/5
 Disallow: /
 
 User-agent: Mozilla/4.0 (compatible; MSIE 4.0; Windows NT)
 Disallow: /
 
 User-agent: Mozilla/4.0 (compatible; MSIE 4.0; Windows 95)
 Disallow: /
 
 User-agent: Mozilla/4.0 (compatible; MSIE 4.0; Windows 98 )
 Disallow: /
 
 User-agent: Teleport
 Disallow: /
 
 User-agent: TeleportPro
 Disallow: /
 
 User-agent: MIIxpc
 Disallow: /
 
 User-agent: Telesoft
 Disallow: /
 
 User-agent: Website Quester
 Disallow: /
 
 User-agent: WebZip
 Disallow: /
 
 User-agent: moget/2.1
 Disallow: /
 
 User-agent: WebZip/4.0
 Disallow: /
 
 User-agent: WebSauger
 Disallow: /
 
 User-agent: WebCopier
 Disallow: /
 
 User-agent: NetAnts
 Disallow: /
 
 User-agent: Mister PiX
 Disallow: /
 
 User-agent: WebAuto
 Disallow: /
 
 User-agent: TheNomad
 Disallow: /
 
 User-agent: WWW-Collector-E
 Disallow: /
 
 User-agent: RMA
 Disallow: /
 
 User-agent: libWeb/clsHTTP
 Disallow: /
 
 User-agent: asterias
 Disallow: /
 
 User-agent: httplib
 Disallow: /
 
 User-agent: turingos
 Disallow: /
 
 User-agent: spanner
 Disallow: /
 
 User-agent: InfoNaviRobot
 Disallow: /
 
 User-agent: Harvest/1.5
 Disallow: /
 
 User-agent: Bullseye/1.0
 Disallow: /
 
 User-agent: Mozilla/4.0 (compatible; BullsEye; Windows 95)
 Disallow: /
 
 User-agent: Crescent Internet ToolPak HTTP OLE Control v.1.0
 Disallow: /
 
 User-agent: CherryPickerSE/1.0
 Disallow: /
 
 User-agent: CherryPickerElite/1.0
 Disallow: /
 
 User-agent: WebBandit/3.50
 Disallow: /
 
 User-agent: NICErsPRO
 Disallow: /
 
 User-agent: Microsoft URL Control - 5.01.4511
 Disallow: /
 
 User-agent: DittoSpyder
 Disallow: /
 
 User-agent: Foobot
 Disallow: /
 
 User-agent: WebmasterWorldForumBot
 Disallow: /
 
 User-agent: SpankBot
 Disallow: /
 
 User-agent: BotALot
 Disallow: /
 
 User-agent: lwp-trivial/1.34
 Disallow: /
 
 User-agent: lwp-trivial
 Disallow: /
 
 User-agent: Wget/1.6
 Disallow: /
 
 User-agent: BunnySlippers
 Disallow: /
 
 User-agent: Microsoft URL Control - 6.00.8169
 Disallow: /
 
 User-agent: URLy Warning
 Disallow: /
 
 User-agent: Wget/1.5.3
 Disallow: /
 
 User-agent: LinkWalker
 Disallow: /
 
 User-agent: cosmos
 Disallow: /
 
 User-agent: moget
 Disallow: /
 
 User-agent: hloader
 Disallow: /
 
 User-agent: humanlinks
 Disallow: /
 
 User-agent: LinkextractorPro
 Disallow: /
 
 User-agent: Offline Explorer
 Disallow: /
 
 User-agent: Mata Hari
 Disallow: /
 
 User-agent: LexiBot
 Disallow: /
 
 User-agent: Web Image Collector
 Disallow: /
 
 User-agent: The Intraformant
 Disallow: /
 
 User-agent: True_Robot/1.0
 Disallow: /
 
 User-agent: True_Robot
 Disallow: /
 
 User-agent: BlowFish/1.0
 Disallow: /
 
 User-agent: JennyBot
 Disallow: /
 
 User-agent: MIIxpc/4.2
 Disallow: /
 
 User-agent: BuiltBotTough
 Disallow: /
 
 User-agent: ProPowerBot/2.14
 Disallow: /
 
 User-agent: BackDoorBot/1.0
 Disallow: /
 
 User-agent: toCrawl/UrlDispatcher
 Disallow: /
 
 User-agent: WebEnhancer
 Disallow: /
 
 User-agent: TightTwatBot
 Disallow: /
 
 User-agent: suzuran
 Disallow: /
 
 User-agent: VCI WebViewer VCI WebViewer Win32
 Disallow: /
 
 User-agent: VCI
 Disallow: /
 
 User-agent: Szukacz/1.4
 Disallow: /
 
 User-agent: QueryN Metasearch
 Disallow: /
 
 User-agent: Openfind data gathere
 Disallow: /
 
 User-agent: Openfind
 Disallow: /
 
 User-agent: Xenu's Link Sleuth 1.1c
 Disallow: /
 
 User-agent: Xenu's
 Disallow: /
 
 User-agent: Zeus
 Disallow: /
 
 User-agent: RepoMonkey Bait & Tackle/v1.01
 Disallow: /
 
 User-agent: RepoMonkey
 Disallow: /
 
 User-agent: Zeus 32297 Webster Pro V2.9 Win32
 Disallow: /
 
 User-agent: Webster Pro
 Disallow: /
 
 User-agent: EroCrawler
 Disallow: /
 
 User-agent: LinkScan/8.1a Unix
 Disallow: /
 
 User-agent: Keyword Density/0.9
 Disallow: /
 
 User-agent: Kenjin Spider
 Disallow: /
 
 User-agent: Cegbfeieh
 Disallow: /