I've heard good things about the 16 euro hostel, near old town and centrally located:

http://www.16eur.ee



Also Hotel Go Schnell by the train station is cheap, sometimes 20 euro. www.gohotels.ee

smallEdited: 2:29 pm, January 02, 2011/small

Dzingel hotel is quite far from centre (considering Tallinn).

There are for example Tatrari 53 hotel (special price 30 eur, http://www.tatari53.ee/); Dorell www.dorell.ee,

This is obviously a problem with euro changeover and booking via hostelworld site. I went to the site and it quoted me 250 eek (former estonian currency) which is equal to 16 euro.