One of the best strategies to gain back links is to bookmark your website in dofollow social bookmarking sites.

Here is a list of social bookmarking sites (with their page rank).

1 - http://slashdot.org (PR9)
2 - http://digg.com (PR8)
3 - http://technorati.com (PR8) (Only Blogs)
4- http://www.furl.net (PR7)
5 - http://www.backflip.com (PR7)
6 - http://www.hugg.com (PR7)
7 - http://www.mixx.com (PR7)
8 - http://ma.gnolia.com (PR7)
9 - http://www.connotea.org (PR7)
10 - http://mystuff.ask.com (PR7)
11 - http://www.reddit.com (PR7)
12 - http://www.dzone.com (PR7)
13 - http://www.folkd.com (PR7)
14 - http://multiply.com (PR7)
15 - http://www.searchles.com (PR6)
16 - http://de.lirio.us (PR6)
17 - http://www.dotnetkicks.com (PR6)
18 - http://www.bloghop.com (PR6)
19 - http://www.plime.com (PR6)
20 - http://www.bibsonomy.org (PR6)
21 - http://www.clipclip.org (PR6)
22 - http://linkagogo.com (PR6)
23 - http://www.spurl.net (PR6)
24 - http://www.zlitt.com (PR6)
25 - http://www.indianpad.com (PR6)
26 - http://www.tumblr.com (PR6)
27 - http://www.myvmarks.com (PR5)
28 - http://www.listible.com (PR5)
29 - http://www.bringr.com (PR5)
30 - http://faves.com (PR5)
31 - http://www.linkinn.com (PR5)
32 - http://spotback.com (PR5)
33 - http://www.mylinkvault.com (PR5)
34 - http://my.xilinus.com (PR5)
35 - http://linkatopia.com (PR5)
36 - http://www.bumpzee.com (PR5)
37 - http://www.bookmarktracker.com (PR5)
38 - http://www.healthranker.com (PR5) (Only for health related websites)
39 - http://www.a1-webmarks.com (PR4)
40 - http://www.wirefan.com (PR4)
41 - http://www.bmaccess.net (PR4)
42 - http://blogmarks.net (PR4)
43 - http://www.diigo.com (PR4)
44 - http://www.oyax.com (PR4)
45 - http://socialogs.com (PR4)
46 - http://www.contentpop.com (PR3)
47 - http://www.pixelmo.com (PR3)
48 - http://www.memfrag.com (PR3)
49 - http://getigadget.com (PR3)
50 - http://www.jumptags.com (PR3)
51 - http://www.plugim.com (PR3)
52 - http://www.syncone.net (PR3)
53 - http://postonfire.com (PR3)
54 - http://www.business-planet.net (PR3)
55 - http://www.hatedorloved.com (PR3)
56 - http://www.bookmarks.com (PR3)
57 - http://www.yattle.com (PR2)
58 - http://www.kapely.net (PR2)
59 - http://www.givealink.org (PR2)
60 - http://totagit.com (PR2)
61 - http://socialblink.com (PR0)
62 - http://wigleytagz.com (PR0)
63 - http://buzztagz.com (PR0)
64 - http://youtagz.com (PR0)
65 - http://space-ed.com (PR0)